Hack the Vote

I don't think much of hacking challenges in general.
They can prove a system is vulnerable, but they cannot
prove that it is not. In other words, if you're successful, there's obviously a problem, but if you're unsuccessful, maybe you just didn't hit on the magic combination.

That being said, here's a hacking challenge that might be worth looking into. Rebecca Mercuri's challenge to e-voting machine vendors to open themselves up to scrutiny by the security community is on the money, even without the $10,000 prize.