Deep Impact is scheduled to launch in about 80 minutes from now (at 1:47 PM, East-coast time). Deep Impact is a mission that will, for the first time, give astronomers a glimpse of the inside of a comet. Up to now, we have only been able to study the crust, but Deep Impact is sending a one-ton (or so) battering ram to Comet Temple I. They will then be able to study ejecta from the impact to see what’s under the surface.
You can follow the launch by following the links on the Deep Impact Homepage. Here’s wishing for a successful launch!
UPDATE: It launched at 1:47 Eastern time. Check out the NASA Deep Impact page for launch footage.