It's no secret that I've been pretty much disgusted with the Democratic Party for a long time and occassionally indulge in fits of pique where I want to put the fear of the electorate in them. While I've never counseled not voting at all, I have had my days where I think, the hell with it, I'm voting third party. Why vote for Democrats if they vote like Republicans when they get into office? However, as Avedon notes this is a somewhat politically suicidal way to teach the Democratic party a lesson and has a more practical suggestion.
Assuming there is going to be an election in 2008, making primary challenges where possible, electing real progressives at every level (doesn't matter what party - if they are progressives and they can win, then help them win; let a hundred Bernie Sanderses bloom), has to be a priority.This is certainly the best place to start and over the long term is a plan with the best chance of populating the Beltway with progressive politicians who are responsive to the will of the people.
I think we also have to work on reforming how the campaigns are run in the first place though. As long as the field is limited to only those who can raise large amounts of cash, deep pocket contributors will continue to dictate policy. I'm a late convert to the concept, but mandated public financing as a way to level the playing field is looking more attractive to me all the time.