Not sure how many of you know or are interested, but here you go:
Reuters) - The first of a pair of robots is ready to launch from Cape Canaveral on Sunday, joining a scientific armada headed for Mars in an international effort to determine if life exists or ever existed on Earth's neighbor. The first of two Mars Expedition Rovers, robots about the size of riding lawn mowers, sat atop a Delta 2 rocket scheduled for launch at 2:05 p.m. EDT on Sunday. Its twin is scheduled for launch on June 25. They join Japanese and European satellites on their way to the red planet and two NASA satellites already orbiting Mars
Here is a nice picture sequence of the way they want things to happen.
http://mars.jpl.nasa.gov/mer/mission/launch_e_sequenceDef.html
Here's a site I found that has a countdown clock. I'm sure NASA has one somewhere on their site, but I didn't see one. Current 5hr & 30 minutes to launch.
http://www.space.com/marsrover/