That sucks. Anyway, when you say that it just humms, you're talking about the electric motor, I assume. More than likely, one of the capacitors on the motor blew. You can replace it yourself, but you have to be careful because even with the power off to the motor, these capacitors contain alot of voltage, much like a battery but they will discharge all at once if grounded.
I'd remove the drivebelt and then try to turn the compressor pump by hand first to make sure it wasn't something mechanical there. Then, remove the cover(s) on the capacitors. I've read where they recommend you bleed off any voltage on the capacitors with a wire that has a small resistor installed on it. You'd best do a search online for advice on this if you can. Then after you do this bleed off, remove the two leads on the capacitor, take an ohm meter and do a test on the capacitor. What will happen is the capacitor will take some power from the ohm meter battery supply and the resistance will change as it's hooked up. Then hook the ohm meter leads reversed from how you just did it, the reading you just took will reverse itself. There are also some multimeters that have selections just for testing capacitors.
I know, confusing, and I'm sorry I'm not too good at explaining this, hopefully someone else will give you a better explanation.