They're made by KB Covers - - www.kbcovers.com - - just happened to buy one last week, already finding all kinds of dirt, crumbs, and dust that's not getting into the innards of my laptop...

There are even more options available on the kb covers website including dvorak, european, large font, world of warcraft, etc...

They employed a lot of the tricks (Rubes?) that are used by the folks on the japanese kids' show Pythagoras Switch -- check a bunch out here, and the rest here.

The Mythbusters tried one of these and said it was totally bogus.