UPDATE: We have discontinued our use of UserVoice as of 12/11/2008
We've been trying to figure out a good structured and fair way of getting user input. We were pointed to UserVoice.com by Greg Heller at NTEN. UserVoice seems a fairly simple Web 2.0 site which does exactly that. Hopefully it has a decent search / sort / categoization system to handle an expanding list of features.