You could leave it in dry rice for a while, if you can find a big enough tub...
It's more practical with smaller gadgets, but the rice draws out any moisture.
With the Macbook's having a unibody casing I'd imagine it's harder for the moisture to get out as there's limited air gaps etc..
Leave it open in a largish box with a couple of those bags of beady things (silica balls) you get in electronics packaging. Will be dry in a day.
Well after leaving it with 10 silcon gel sachet's donated by the Science department, in a sealed bag, it now boots at normal speed, and the fans do not come on anymore and all is normal apart from the trackpad :( its just not responding to my finger and its jumping stuff all over the screen by its self.
So just put it back in and hope its more moisture to be sucked out, but worst case i am guessing its no longer a case of needed a new logic board.
If it's just the trackpad, trackpad boards can be sourced off eBay and self-fitted, or buy an Apple Magic Trackpad connecting by bluetooth.