The passage of ObamaCare is currently trading at a 50% probability on Intrade:
Note that the graph above is closing prices only. The current market is 50, meaning that the "crowd" says passage is a coin flip. Yesterday, in the wake of Obama's remarks (see: "to hell with the Republicans") the market traded briefly at 90. So the volatility around this is exceptional.
I put the odds around 25%. This still has to go through the House again where it first passed by only 5 votes. Since then, there's been a death, a resignation, and a Republican - the lone yes vote from the GOP - who has reversed himself. Then you have the Stupak Twelve who won't vote for the Senate measure on abortion grounds. It gets worse from there. Tough sledding for Pelosi and the Majority Whip, although no one is suggesting she's not tough.
I wrote a piece in January called "How Now, President O?" that took the view that the president would not tack to the center, a la Bill Clinton circa 1995, to salvage his presidency. I think the jury has come back on that one: ideology has trumped public image.