Cleaning Your Keyboards?

myKeyb0ardsAreD1rty asks: "Okay, I am a little bit messy, but never have I been a dirty person. Nonetheless, looking at my computers, I get the feeling I am. My beloved Microsoft Ergonomic Keyboard's keys have ugly black marks after 5 years of continious use (and I like this keyboard, I don't want another one). The same happened to keyboards used by others in this office. I do clean my keyboard from time to time, but now, I just cannot get it clean anymore. I have seen similar stains in other offices, so it must be a common problem. How do folks clean their computers to get rid of this?" We did a topic on cleaning computers back in June, but the tips there were more on generic computer cleaning. What specific suggestions do you have for cleaning what is probably the dirtiest part of your computer?