Rishi Gautam was married to Ahalyaa, the daughter of Mudgal, a Paanchaal King. Mudgal was in the lineage of Raajaa Bharat >> Rantidev. Gautam and Ahalyaa had three sons named Vaam Dev, Nodhaa and Shataanand. Among them Vaam Dev was one of the Rishi with Soorya Vansh - Raajaa Dasharath, Shataanand was the Purohit of Raajaa Janak in Janak Puree, in Mithilaa. Shataanand had the son named Satyadhriti and his son was Maharshi Sharadwaan. One day Maharshi Sharadwaan saw Urvashee Apsaraa and his semen fell on a bush of Moonj. It caused to born a boy and a girl. Mahaaraaj Shaantanu saw them and brought them home and brought them up. He named them Kripaa and Kripee. Kripaa became the Kul Guru of Kaurav and Paandav and Kripee was married to Aachaarya Drone who taught weapons knowledge to Kaurav and Paandav.
All his three sons were the seers of Mantra. There is a hymn called Bhadraa in Saam Ved which is attributed to Rishi Gautam.
Gautam's 60-year old penance is described in Mahabharata, Shaanti Parv.
Naarad Puraan also describes a 12-year long famine in which Gautam fed the Rishi and saved them.
Devee Bhaagvat relates Godaavaree River with Gautam Rishi.
The Tryambakeshwar Jyotirling is there because of Rishi Gautam.
Some famous disciples of Maharshi Gautam were Praacheen-yogya, Shaandilya, Gaargya and Bharadwaaj.
Gautam has written Dharm Sootra also, containing 28 chapters with 1,000 aphorisms - the oldest book on Dharm.
Gautam shares the Angiraa ancestry with Bharadwaaj
Who was Ahalyaa? - Another Version
Once it happened so that Brahmaa Jee took the best of every creature and created a woman and named her Ahalyaa. Brahmaa was very happy to see her. He was so much happy that he himself started staring at her. She was going around the Dev Sabhaa. In whichever direction she went Brahmaa started looking at her in the same direction. Since she went in all the directions, Brahmaa Jee had to have four faces to look at her in all the directions. All Devtaa were also noticing this. Seeing this Brahmaa Jee came to himself and to save himself from her temptation he gave her to Maharshi Gautam to serve him. Ahalyaa stayed with him for a long time and served him well for many years. After that Brahmaa finally gave her to Rishi Gautam and Rishi Gautam Jee married her. Indra was also attracted to her since she was created and he had her in his mind since then but as Brahmaa Jee gave her to Rishi Gautam, he was not happy. He was always thinking about Ahalyaa.
Ahalyaa-Indra Incident - One Version
Well, Ahalyaa was very beautiful. Since Indra saw her he wanted to have her. According to this version, Ahalyaa had also seen Indra in the Dev Sabhaa and she was also attracted to Indra, but she could not disobey Brahmaa Jee so she went with Rishi Gautam. Thus Ahalyaa was also attracted to him. So one day Indra asked Chandramaa to help him. CHandramaa agreed. The plan was that Gautam Rishi used to go for his morning ablutions at about 4 am. On that fateful day Chandramaa and Indra would go there together. Chandramaa would take a form of a cock and crow at 2 am, and when Muni would go for his daily chores early in the morning, Indra would come in the form of Gautam and had her. So on that day Chandramaa assuming the form of a cock crowed before the usual time of cock's crow. Muni did not know it so he rose and went out early, but as he was on his way he felt something fishy. He was suspicious that how come that the crow crowed today so early, but he didn't pay much attention to it.
But when he returned home, he saw Indra coming out of his hut. He understood everything. He gave Shaap to Ahalyaa that she should become a stone. On asking forgiveness of Ahalyaa he reduced the Shaap to "that when Raam will incarnate in Tretaa Yug, and He will touch you with His foot, you will regain your beauty and life and will come to me." And he gave Shaap to Indra that "he should lose his manhood". Ahalyaa became the stone and waited till Raam incarnated on Prithvi and touched her with His foot; but Devtaa became very worried with Muni's Shaap to Indra. So they went to Brahmaa Jee and prayed him to help Indra.
Ahalyaa-Indra Incident - Another Version
According to the other version Ahalyaa was sinless. She did not know that the coming person was Indra. Since he was in the form of Muni Gautam, she thought that Muni had come back early. She was in fact highly surprised to see him come back from his chores so soon, and asked him the reason also. Muni told her that he wanted to make love with her that is why he had come back. Although Ahalyaa could not digest this reason, because that was not the time for it, and since she was a Pativrataa woman, she could not say no to him. They had a good time and when the impersonated Gautam Rishi got ready to go again for his daily chores, he showed her his real form - of Indra. Seeing this Ahalyaa got frightened and asked him to get out of the hut immediately, but unfortunately Gautam Rishi was coming back at the same time as he was going out of the hut, so both got trapped.
With this version Gautam Rishi gave Shaap to Indra that since he came there with the desire of the lust, he should have thousand marks of the woman's vagina all over his body. Indra got very ashamed of this Shaap. He then did severe Tap for Shiv Jee and Shiv Jee gave him Var that those marks would change into thousand eyes. Since then Indra has been called thousand-eyed Indra.
It is said that after this incident with his wife, Gangaa told Rishi Gautam that he should not need to go anywhere for his daily chores and she came very near to his Aashram.
Gautam Brings Gangaa
Taken from http://rootshunt.com/gautam.htm Read a similar story How Godaavaree River Descended?
Once a natural drought occurred and the rain did not fall for 100 years. All vegetation became dry, earth's surface became too dry to produce anything, so Gautam did penance to bring water on Earth to comfort Earth's creatures. He pleased Varun Dev, because he was the Devtaa of water, and when he appeared before him he asked him to rain for the benefit of the world. But Varun said - That it all was in the hands of Shiv, and he should ask him only that thing which he can give to him. At this Gautam asked him an Akshaya Kund of water. Varun asked him to dig a pond and put an everlasting lotus flower in it, so that the pond is always filled with water. Rishi Gautam dug a pond, Varun filled it with water and blessed that pond - "This pond will always have water up to the area of one arm's length and whoever will serve this pond will get his wishes fulfilled."
Rishi Gautam started farming with that water. The news spread and people started living near that pond. Because of Varun's blessings the pond never dried. Once Gautam Rishi drew water from that pond urgently, so his students came to fetch water from that pond. Some Rishi's wives also came to take water at the same time. Rishi's wives requested the disciples to take water after they had taken water from the pond. The disciples felt insulted and they told Ahalyaa that Rishi's wives did not let them fetch water from the pond. Hearing this Ahalyaa herself came with them and let them take water and went away. Seeing this Rishi's wives also got angry and told some false things to their husbands.
In turn Rishi wanted to teach Gautam a lesson. They could not teach him the lesson on his own so they started worshipping Ganesh Jee. Ganesh Jee got pleased, appeared before them and said - "O Rishi, Your intention is not good, you should not bring destruction at your hands." Rishi said - "We are insulted without any reason, that is why our wish should be fulfilled." Ganesh Jee again said - "Since Gautam Rishi is blessed by Shiv, so he will remain unharmed but since your intention is bad, you will be in great difficulty." After saying this Ganesh Jee disappeared.
Then one day Ganesh Jee appeared as a sick cow and started grazing on Gautam's field. Coincidentally Gautam was near his field, so he saw a cow spoiling his crop. He tried to make her go but when she did not go just like that, he took a straw a grass and touched her body with it to make her go. Unfortunately the as the straw touched to cow's body, she died. All this was planned so as soon as the cow died, the other Rishi soon gathered there and blamed Gautam and their wives blamed Ahalyaa for the death of that cow. They all decided that nobody should even see the face of Gautam like Rishi; and they made Gautam Rishi, his wife and disciples move from that place. Rishi Gautam went one Kos away from that spot. Gautam was also very sad after the death of the cow, so he decided that until he will clear of this sin, he will not touch anybody and will not do any religious ceremony. This period was very painful for him.
After 15 days Gautam Rishhi went to those Rishi and asked them to clear the cow killing sin. Seeing the condition of Rishi Gautam, the other Rishi felt pity on his, but because of their ego they said to him - "Since your disciples and wife have insulted our wives they have to bear the consequences. Only Lord Shiv will free him from this sin. For this he has to go around the earth and call loudly out about your sin; after that he should keep fast for one month and circumambulate 100 Braahman. Then only you would be free from your sin. After this he should make Gangaa appear at this place, take bath in her, make 1 Crore mud Shiv Ling (Paarthiv Poojan) and start meditate on him." Gautam did it and pleased Shiv Jee. Shiv Jee got pleased and appeared before him with Paarvatee and his Gan and asked him to ask for a boon. Gautam said - "If you are pleased, please release me from my sins." Shiv said - "You were cheated and were given so much stress for the sin you have not committed. Those Braahman will have to suffer for this, They will have only fake knowledge, because whoever harasses my devotee can never be happy."
Gautam was very kind, he said - "Those Braahman are innocent, because, because of them only he could see him. But I will be very happy if you give me Gangaa from your head." Shiv put down Gangaa from his head and giving her to Gautam he said to Gangaa - "From today Gautam will serve you and you wash away his all sins." Gangaa said - "I will surely follow your orders, I will purify Rishi and his family and then go back to my place." Shiv Jee said - "You stay here till the beginning of Vaivaswat Manvantar." Gangaa said - "I will stay here till then only when I will be worshipped here and Shiv, Paarvatee and his Gan will stay on my banks." All Devtaa got very happy to hear this, they said - "When Brihaspati will be in Sinh Raashi (Leo Sign), her importance will spread in the three Lok. After 12 years when the Time comes, and people will come there, take holy bath there, and visit Shiv temple, they will be free from their sins."
So Gangaa flowed from Brahm Shail (Vindhya Giri) through Udumber branch and flowed in the form of River Gautamee. This source of that river is called Gangaa Dwaar. Gautam Rishi, his disciples , and Ahalyaa took bath in it, worshipped Shiv Ling and got free from their sins. but when the Rishi who blamed him came to take bath, she disappeared. At present this pace is called Panchvatee in Naasik.
During the last days of Brahm Shail, Gautam and Ahalyaa came there. When Ahalyaa was taking bath there, Rishi got attracted to her and looked at her with desire. This sight made her pregnant and gave birth to a baby girl Anajanee. When Gautam moved from Brahm Giri, Anjanee was 9 months and 27 days old.
Gautam Moves to Chandrabaanee
Taken from http://rootshunt.com/gautam.htm
Gautam, Ahalyaa and their daughter lived at Brahm Giri (Naasik) for some time. Those other Rishi used to come there to visit but they were jealous with him for his simplicity. When they threw stones on him, they became flowers to Gautam. After the birth of Anjanee, Gautam moved to Chandrabaanee, in Uttaraakhand region. Chandrabaanee is also considered Dronaachaarya's in-law's place, means Ashwatthaamaa's mother's place, means Kripee and Kripaachaarya's place.
Here it is written that Ahalyaa cursed Anjanee to be a virgin mother, because she spoke to Gautam Rishi against her. In fact all the three information, that Anjanee was the daughter of Gautam and Ahalyaa, and that she was cursed by her mother, and that the curse was to become the virgin mother; are new to me.