Keys on a keyboard tend to pick up a weird, grey coating over years of use - hundreds of thousands of finger taps are bound to leave a mark. If it really bothers you, you could always buy an external keyboard, but on the road this is too impractical to lug around.
Filling in for those mobile moments is this iSkin keyboard cover. It rolls up into a ball and even scrunches while you carry it around, and then rebounds to one flat surface to cover the keys. The covers are sold for MacBooks and MacBook Pros, but ours also fitted a PowerBook perfectly.
The sheet is moulded to the keyboard's shape, so it doesn't slide about. It's very thin and easy to type through, and doesn't seem to press on the screen with the lid down. Its only major downside, ironically, is it's the kind of sticky rubber that picks up dirt easily.
We found ourselves washing it down after just one trip, and all we did was scrunch it into a pocket. It's a magnet for filth, but it does keep the keyboard clean. A few different colours are available, too. James Ellerbeck