My keyboards and mouse get filthy quickly. Big globs of dirt are on several of the keys, especially home row. There must be something in the oils my fingers secret or something, because my clarinets always had the same problem when i was in school. I've given up trying to keep my keyboards clean because it would be at least a weekly effort. I imagine that it would be pretty gross to anyone else using my computer though.
My iphone (and ipod before it) though, I clean the screen with rubbing alcohol at least once a week. I can't stand looking at the fingerprints on it. And I've also read that it's one of the germiest thiings that many people touch regularly.