I don't know that voter registration lists are available to the public, but there are certainly lots of organizations who try to challenge them (hoping to knock out voters who will have a harder time renewing their registrations and who may have voted against the party the organization represents.) Nasty business.

You can see who people donate to, assuming normal donations, because you have to give some background (are you employed, where, what party are you registered in, and in that instance it may show when you last voted.) PACs and huge money donors live in an entirely different world.