There's Buddy Roemer. He's better than pretty much all other candidates including Ron Paul when it comes to campaign reform. No superpacs. 100 dollar donation limit. It's in every citizens interest(regardless of party affiliation) to make money less influential in politics.

Buddy Roemer on MSNBC's Morning Joe: http://www.youtube.com/watch?v=8oMoAMnFczY

Then there's Lawrence Lessig. He's not a politician but he's also working to limit systemic political corruption.