2010 Election Interactive Maps
The New York Times has their 2010 Mid-Term elections interactive site in place. From here you can view all of the House of Representatives, Senate and Gubernatorial races in all the states and districts, as well as a calendar of all the remaining primaries, and of course results in November.
Most of the states and districts naturally lean towards Republican or Democrat, but several states and districts are still considered a "toss-up". Those will be the ones to watch.
Via The Map Room