Nothing big, but I know that some people have really dusty keyboards and don't know how to clean them efficiently. Anyway, to clean a keyboard, take all of the keys off and put them into a big bowl water and let them soak for about 5 minutes. If not in a hurry to use the PC, let the keys air dry. If in a hurry, blow the water out with the mouth and wipe them with a towel or cloth. To clean the keyboard bed, take a cue tip and put some alcohol on it, and then simply rub it between all of the holes for the keys.
My laptop keyboard is rank, but I'm afraid that I won't be able to get the keys back on if I pry them off. derp
Yes, this applies to tower PC keyboards. For laptop keyboards, I'm not sure. There are also those clear keyboards that can actually be dunked in the water, as long as the power area doesn't touch the water.
You can buy special cleaning kits for laptop keyboards. They come with a special brush and a solution used specially for cleaning the keys etc. As for the keys coming off thing, I believe you can click them back on like any other keyboard. At least, I can with my laptop. I dunno if it varies for others lol
I know my laptop keys can click on and off, i found this out the hard way once playing Flash Flash Revolution, when my nail caught under one of the arrows keys and managed to pry it right off. I haven't tried much to get in between keys yet (might go look for the kit Bushy mentioned) but every so often I do swipe them with an alcohol prep pad (having a nurse as a mom is a plus since she can bring home dozens of them for me). They also work well on my laptop's screen.
