I personally believe the most important way the Democrats can defeat Bush is to get more people to the polls. Obviously, part of this requires delivering a message that will motivate people to vote, but a lot is simply grassroots mobilization — something the Republicans, especially the far right, has been very good at.
There are a number of organizations mobilized to do this, and as a result of recent changes in campaign finance laws, these organizations have become even more important:
America Coming Together (General voter outreach to combat Bush.)
Partnership for America’s Families (Backed by organized labor. Has been effective at targeting crucial minority votes in recent local elections.)
SouthWest Voter Representation Project (Targets Latinos, does not appear to be a partisan organization.)
Emily’s List (A Pro-Democrat, Pro-Choice program to mobilize women voters.)
The best thing you can do is to give these organizations your time, but if you can’t do that, give them your money!!!
UPDATE: A good article about these groups (and more) from In These Times:
About a dozen groups—backed by the likes of Emily’s List, the AFL-CIO, the Sierra Club and MoveOn.org—are quietly building an infrastructure to undertake the most extensive door-to-door grassroots voter contact operation in U.S. history. Its potential to turn the election already is well understood on both sides: Longtime activists say they haven’t felt this energized in decades—and Republicans are using congressional hearings to shut down the operation or steal directly from its playbook.