ThinkProgress has a running count of where Congress members stand on the President's plan to increase troop levels in Iraq. Their interactive list lets you see where each member stands and where ThinkProgress got their information.
Using statements in news releases, to the media, and constituent letters, they've identified where 414 of the 535 members stand.
At last count, 242 members oppose the plan, 107 support it outright. (ThinkProgress)