Google Election Maps:

This Google page lets you see state-by-state breakdowns, with vote totals within each state, and also county-by-county breakdowns, if you click on the state and then click on "County Map" in the upper right-hand corner of the pop-up window.

If you have Google Earth installed, you can just go to this page and click on "Download Historical Voting Results" in the right sidebar. Thanks to Prof. Jim Gibson for the pointer.