You can start with the voting records on various bills:
http://www.senate.gov/pagelayout/leg...sers/votes.htm
That to me is about as unbiased as you're going to get because it is what it is. The thing is that you have to know what you're looking at. For example, you can't say Obama voted for infanticide. . .unless you know the context of the entire bill. But it's all right there.
Snopes is good at refuting or confirming some of the more ridiculous notions and rumors floating around.
http://www.votesmart.org/program_about_pvs.php They don't take money from special interest groups or support one candidate over another.
http://knowbeforeyouvote.com/ This site is excellent because it has side by side comparisons.
And lastly, although it's not necessarily unbiased. . .I read the candidates' websites. If you go under their issues you can read about their major running platforms.