I have begun to rely on the Vote View website as a basic tool for my undergraduate students. It’s a wonderful way to gain insights into current and historical politics in the U.S., and it’s just a lot of fun.
VoteView has gone mainstream–it was cited on Rachel Maddow and I regularly see references among the smarter commentators on American economics and politics.
This, however, is going a bit too far! http://www.polarizedpolitics.com/#!polarized-politics/mainPage.
(I think Keith is actually not associated with this site, but who knows?)