How picky are you?
I'm pretty sure that seely's right. If you have a steel frame, you can usually just bend it back with your hand and get it straight enough to ride home. Generally, you're looking to get the derailleur arm to hang straight down. Be sure to leave the derailleur bolted onto the frame when you bend it or you may deform the threaded hole that it bolts onto.
If you have an aluminum frame, the first question to ask yourself is: "Can I possibly ride it the way that it is?" If the answer is "Yes," make do and be on your way. If the answer is "No," you don't have anything to lose do you? Go ahead and try to bend it back. If the hanger snaps off that might be God's way of telling you that your bike should be a single speed.
Good luck.