Voter Activation Network--the voter-information database company that designed the interfaces for the voter lists maintained by the Democratic National Committee, America Votes (using the Catalist database), and more, and which has previously used Palm Pilots to help canvassers--now has an iPhone app.
It's called MiniVAN Touch (hah! Minivan.) and it's available on the App Store; it works on the iPhone and iPod Touch platform.
VAN databases are disseminated by progressive groups, for instance, to Democratic campaigns, and VAN-created interfaces are commonplace; meaning this iPhone app has the potential to be very widely used by Democratic campaigns.