If we accept all the Star Wars films as the same canon, then a lot that happens in the original films has to be reinterpreted in the light of the prequels. As we now know, the rebel Alliance was founded by Yoda, Obi-Wan Kenobi and Bail Organa. What can readily be deduced is that their first recruit, who soon became their top field agent, was R2-D2.
Via Jason Kottke [1], “A New Sith, or Revenge of the Hope Reconsidering Star Wars IV in the light of I- III [2]”
An interesting reinterpretation of Star Wars IV–VI [3], notwithstanding the fact that George Lucas [4] was making everything up as he went along, especially for episodes I–III [5] but he doesn't care—he's got our money and besides, geeks live for explaining continuity errors in science fiction series (and amusingly enough, nothing that went on in Episodes I–III matched what he wrote about in “Bantha Tracks [6]”—I know this because my friend Hoade used to get this newsletter as a kid).
[1] http://www.kottke.org/remainder/07/01/12564.html
[2] http://www.morningstar.nildram.co.uk/A_New_Sith.html
[3] http://www.starwars.com/themovies/
[4] http://www.starwars.com/bio/georgelucas.html
[5] http://www.starwars.com/themovies/
[6] http://www.starwarsmags.com/Magazine_Archieves/Offical_SW_Periodicals/S