The American Museum of the Moving Image has a cool site with all of the Presidential television ads (I think in history). The ads begin with the 1952 Presidential campaign and continue through to today. The site is constantly being updated as the new ads come out this year. The best part about the site is the ads are viewable in their original content. For example some of the ads were changed after opposing campaigns complained. An internet ad earlier this year put out by the Bush campaign showed an imaged of Howard Dean & Al Gore with images of Hitler. Check out the original ads here.