Mobile Voter that lets users register to vote by sending an SMS message (more specifically, the user texts a CSC, Mobile Voter determines the appropriate district and then mails the correct forms to the user to sign and send back).
http://www.mobilevoter.org/
from Bart Cheever....
We just launched our first major trial in San Francisco. We've got billboards and taxi tops up around the city and have had musicians onstage at local concerts telling people in the audience to take out their phones and register to vote on the spot, which has been phenomenally successful.
We were able to mail out a bunch of forms in time for the registration deadline for the upcoming election and will follow up with SMS messages next Tuesday reminding people to actually vote (eventually we'll be able to SMS people specific polling locations).