MoveOn.org's online primary was covered extensively by The Note and others in the more "mainstream" media, but its worth taking a look at them. They not only registered and encouraged over 300,000 people to vote in an unprecedented online effort, but they also managed to raise $1.7 million for Dem candidates. I worked for two online "political activist" sites (gone in the crash) during the 2000 election cycle, both venture funded and both with unworkable business models. MoveOn, begun as a liberal response to Republican efforts to impeach Bill Clinton, was smart. They started and stayed small and lean, and unlike the other online political sites, they really harnessed the power of the Internet, using technology and the interest of like-minded compatriots to spread their message (and donate money) to whatever cause they were interested in. This successful model will spread across all interest group sectors, and in the post-McCain/Feingold world, will become increasingly powerful.

Also check out the various Dem candidate web sites. Not only informational, but a powerful fundraising tool for the candidates - especially for Howard Dean.