The light novel ended a little differently than the anime. The main light novel ends at Ryuuji beginning his third year of high school and meeting Taiga along his way to school, while the anime ends at their high school graduation, and then meeting Taiga in one of the classroom. In the light novel, she moved to a different, but nearby apartment block and her mother cancelled her drop out application from school. The manga has not been finished yet, so we don't know the ending of it per-se. I wouldn't call it the furthest in terms of plot, as it doesn't really cover their third-year high school life or beyond.
However, there is the Toradora visual novel that does cover what happens after their high school graduation. The Taiga ending reveals her to be with Ryuuji and pregnant.
Taiga's VN ending: https://www.youtube.com/watch?v=odOpaby7Fpk