When Steve Jobs delivers a keynote or other high-profile presentation, Apple typically posts a video of the event on the web and in iTunes (who else remembers when you would stream these things live? Those were the days).
This week they've given these videos an official home in the iTunes Store. The Apple Keynotes Podcast [link] features three videos so far, the MWSF '07 and '08 keynotes plus the March 6th introduction of the iPhone software road map.
Check back on the evening of Monday, June 9th or Tuesday the 10 to see if the WWDC '08 keynote has been made available.