polls, polls and polls.....
Something old. I mentioned this before, but as we all obsess on polls, the best historical compilation of presidential polls is in this from the real numbers guys at Columbia: Presidential Campaign Polls 1952-1992.
Something new: a site that decomplies the political polling beyond anything I have time to digest: http://courses.ttu.edu/hdfs3390-reifman/weighting.htm
and still my favorite, the New School's Parsons Institute for Information Mapping (PIIM) Voting Tool. You really need to try it out by launching the application (click on the map on the left of the intro page).