It's hard to believe that Apple's "Get a Mac" ad campaign is already 4 years old. Since its introduction, the campaign has invited both parody and serious responses from competitors. Plus, poor* John Hodgman and Justin Long can't walk out the door without someone calling them either "Mac" or "PC."
Some have been better than others (the Christmas ads are always a highlight), and Apple keeps several of each year's ads on their site. If you'd like to browse the full history of these ads, check out this page assembled by the folks at AdFreak. They've gathered every TV spot and sorted them chronologically. In case you were wondering, there have been 66 in total. The most ads aired in 2006 (19) and the fewest in 2009 (14).
Enjoy the archive and have fun re-watching your favorites.
*My sympathy is short lived, however. Consider their paychecks.