I've had good luck with some abrasive cleaning stuff, such as SoftScrub. Some brands have bleach included to help with getting the yellow color out, but is harder on the skin. Sometimes you might have to dig out a fine grain sandpaper as well. For keyboards I even pull the keycaps off and clean them individually this way. It's brought back an A1000 from discoloration for me. No, it's not easy, yes it takes a while, and yes it's a good bit of work, but I've been happy with the results, and I'm one of them obsessed loonies out there that has to have it perfect...
