With the creation of The Clone Wars animated series, the characters introduced became canon. So I've been wondering, after the series ended, nothing is ever heard of of Ahsoka Tano. She simply leaves the Jedi Order behind and walks off into the sunset. But what ever became of her? One would think that a former Jedi with that much talent and potential would assist Yoda and Obi-Wan in taking down the Empire. So why did she not resurface after Order 66 was carried out? Why did she not help the Rebels fight the Empire?
She is a member of the Rebel Alliance.
As of Star Wars Rebels Episode 1x13 "Fire Across the Galaxy", we know she is a member of the Rebel Alliance. It stands to reason we might be seeing more of her. (I thought about adding a Rebels tag to the question, but that would negate masking the spoiler - but should probably be done in due time.)
From the canon, we never learned the fate of Ahsoka. After she walked away from the Order, we never learned what happened to her. There are many possibilities:
She was killed by Empire.
She turned to dark side to secretly assist the dark side like Inquisitor.
She heard about Order 66 and went into exile.
She did really assist Rebel Alliances.
Also, I want to point this out that you shouldn't specially treat probable survival of Ahsoka Tano. There were hundreds of Jedi in the Galaxy who survived Order 66 (Kanan is one of them). None of them assisted Rebel Alliances or maybe they did. We just don't know.
She really did assist the Rebel Alliance. Source:
S01E13 of Star Wars: Rebels TV series
Ahsoka Tano was a member of the Rebel Alliance. A key member, in fact, and one of the earliest members.
A year after the Fall of the Republic and Jedi Order, Ahsoka joined Bail Organa's rebellion, arguably the first actual organized groups that were fighting the Galactic Empire. She took over his intelligence network and became the first 'Fulcrum' agent, a specialized rebel intelligence agent. She was vital to the early rebellion, as she was responsible for directing spies and gathering information and using that information to give rebels missions. She was one of the few who reported directly to Bail Organa. Since Ahsoka was the head of early Rebel Intelligence, she (and other Fulcrum agents) were supposed to keep their identities as secret as possible. Only Bail and the Ghost crew knew who she was.
She worked as Fulcrum for 14 years until she was thought MIA on Malachor after her duel with Darth Vader and the subsequent collapse of the Sith Temple. However, Ahsoka survived, and while she was stranded on Malachor for a few years, we can assume she continued helping the Rebel Alliance behind the scenes since she wasn't in the OT. She was confirmed to have survived past the Fall of the Empire and the New Republic Era. She and Naq Med were the only confirmed beings who were fully trained in the Old Jedi Order to have done this.
You can find all this information in the novel, Ahsoka and the tv show, Star Wars Rebels.