I spilled a glass of water on my early 2011 15" macbook pro. The good news is that I'm writing this on that computer.
After turning the machine off immediately, draining the water, checking for moisture inside, and disconnecting the battery I let it dry for a few days before taking it to the apple store. The genius essentially just connected it to a power source and turned it on. It booted, but the fans blew at full speed and it shut itself off while still running firmware.
I tried the same thing at home with the same result, but after a few days I connected it to a power source without pressing the power button and it booted normally. I have restarted it since then.
The battery status reports "replace now" but other than that I can't find any other reports of damaged hardware. However the computer seems overall more sluggish than it should, with chrome occasionally lagging with 2.5 GB of free memory. I tested it a bit with minecraft and I had to change the render distance from far to normal to get decent performance.
I'm also a bit concerned about the temperature sensor, since the behavior with the fans blasting at full speed before the computer turned itself off could be caused by the temperature sensor reporting overheating. I have been careful not to do things that would normally cause the machine to heat up too much.
Is there any way that I can test for problems safely so that I can know what needs to be repaired before the computer is healthy again? I'm running Lion and have no optical drive if that is relevant.