Keyboards are pretty cheap, but before you toss it, run it through the dishwasher. I'm NOT kidding. Just make sure you air dry it for like, 6 days or someting, to make sure it's really dry.
Microsoft warns against it, but I've never come across anyone who's had problems. Besides, if you're going to buy a new one, what have you got to lose?
http://plasticbugs.com/?p=263
or google it, there are tons of sites about this