Maryland experimented with a new voting system last week

Rather interesting. First, each ballot is numbered (they are already so they can account for spoiled ballots). Second, you use a special pen to mark your candidate. When you mark your candidate, a hidden code is revealed, and you can go online and enter your ballot number and verify that your vote was properly counted for the selections that you made.

It's also inexpensive, using high-end commercial scanners, coming in at half the cost of dedicated systems.

http://www.wired.com/threatlevel/2009/11/scantegrity