The nice people who organise NaNoWriMo also now have Script Frenzy - http://www.scriptfrenzy.org/ so if you've always put off sitting down and writing that first draft of the next "Sex Lives of the Potato Men" or bashing out the first few episodes of the new "Lab Rats", then now is your chance.
Basically its 100 hundred pages of script, any script or scripts, in 30 days, 1st - 30 April 2009.
There's no prize except the satisfaction of having done it and a first draft of a script or scripts that you've put off writing...