The STS-121 is due to launch tomorrow (Saturday July 1, 2006). Coverage begins at 10AM Eastern time.
You can tune into NASA TV and watch on the web. You can watch it on your TV too, NASA TV (of course).
These launches never fail to amaze me.
EDIT 1:21 PM PST: Darn it! Scrubbed due to weather. They'll try again Sunday July 2. L