Membrane keyboard recovery: like others have said, try it but don't be optimistic.
When my old Apple USB keyboard (black keycaps, full size function keys, no power switch) started to become a bit sloppy, I tried a few alternatives. The first was a cheap Kensington model: I was never happy with the feel, keys started to stick after three months, not before the keycap lettering wore off. The next was a flat, white MacAlly model: the feel was similar to a bad laptop keyboard, and it never suited me. That's subjective and it may work for you. I finally bought a second hand Apple USB model, the same type that I used in the first place. When it fails, I'll swap it for an ADB Extended Keyboard II plus ADB/USB adapter, assuming that the combination still works in Mac OS X.
On PCs, I've found that some of the cheaper (<£5) Logitech and Cherry models are adequate but unsatisfying for extended use. Spend an extra £5 for the next model up. Microsoft sell good keyboards and mice, but you may find that you need to be a big OEM to get hold of the cheap models. Their £2.50 mouse and £4.00 keyboard are great, but you need to buy 1,000 units or shop around for a seller.
If you live in any country where Mac and PC keyboard layouts differ, think hard before splashing out money on the "wrong layout". Unless you are an expert touch typist AND the OS allows you to remap the keyboard, the differences will drive you nuts. Buy the £5 keyboard with the wrong layout before buying anything more expensive.
When my old Apple USB keyboard (black keycaps, full size function keys, no power switch) started to become a bit sloppy, I tried a few alternatives. The first was a cheap Kensington model: I was never happy with the feel, keys started to stick after three months, not before the keycap lettering wore off. The next was a flat, white MacAlly model: the feel was similar to a bad laptop keyboard, and it never suited me. That's subjective and it may work for you. I finally bought a second hand Apple USB model, the same type that I used in the first place. When it fails, I'll swap it for an ADB Extended Keyboard II plus ADB/USB adapter, assuming that the combination still works in Mac OS X.
On PCs, I've found that some of the cheaper (<£5) Logitech and Cherry models are adequate but unsatisfying for extended use. Spend an extra £5 for the next model up. Microsoft sell good keyboards and mice, but you may find that you need to be a big OEM to get hold of the cheap models. Their £2.50 mouse and £4.00 keyboard are great, but you need to buy 1,000 units or shop around for a seller.
If you live in any country where Mac and PC keyboard layouts differ, think hard before splashing out money on the "wrong layout". Unless you are an expert touch typist AND the OS allows you to remap the keyboard, the differences will drive you nuts. Buy the £5 keyboard with the wrong layout before buying anything more expensive.