Reseat the memory modules, make sure the Battery has a charge and make sure the AC adapter is working and has the proper wattage(usually 60w)... Try removing the battery and AC adapter, then hold the power button for 30 seconds.. then put only the AC adapter back into the laptop and try turning it on. Also, remove HD and wireless card.
If you satisfy all these but the PC still won't boot, then you may have a bad motherboard. Sorry. (Is it under warranty?)
Dampness... as long as it wasn't being used while it was "damp", it probably didn't cause any damage. But I guess it's a possibility. I have had people spill cups of coffee onto a laptop; and once it dries they have no issues... but then again, they may have just gotten lucky.