Have you seen what a plain old bar of Ivory soap will do in the microwave?
If not, you should try it!!!
Before you do anything, though, go watch this video over at Our Best Bites. It will show you what to do to get your soap looking like this (which is really just putting it in the microwave) and then what you can do with it after you've done this.
Okay, even if you don't do anything with it afterwards, it's totally worth buying some Ivory Soap just to watch it puff up like this.
And it makes your kitchen smell really good too.