This google tech talk by Ben Adida describes applications of cryptography and zero-knowledge proofs to voting, and presents a demo "scratch and vote" system designed along those lines.

The video is two years old, in the meantime we had another presidential election that of course used no such thing, but did involve a lot of paper to create a warm fuzzy safe feeling (or maybe not if you thought about it too much).

For the first time, a cryptographically secure voting system was used in a real election in Takoma Park, Maryland, just this month. And since all the data was published, that election has been independently verified.

I've very happy to learn about this stuff.