These two web-sites provide a lot of very useful information.
If you want to know the results county by county of recent Presidential elections or know why James Polk beat Henry Clay in 1844, Dave Leips Atlas of U.S. Presidential Elections has the numbers. Every Presidential election from George Washingtons 1st victory to George W. Bushs re-election is documented here. A note, Leips very useful Electoral College maps are color coded in this way: Republicans in blue, Democrats in Red, as they should be.
If you want to watch every (well, almost every) televion ad in every Presidential Election since 1952, then go to the Online Exhibitions of the Museum of the Moving Image here.
What a country.