Easy to use, effective.
It won't use itself, get going!
Vote With Me matches your phone contacts with an excellent voter file and can show you who you need to turn out in any given election. Given the biggest problem in any election isn't registration, but just getting registered voters out to the polls, this is a crucial tool. It's also much better to get a message from a friend vs. a campaign. The crowdsourcing of who's been contacted through Vote With Me is also a great touch.
As someone who built this in 2011, but using Facebook friends, I know it's a great a tool, but it's up to passionate folks to use it and turn out their friends, it won't use itself. Get going.