1GB RAM chips that fit the 12-inch PowerBook are starting to hit the market. However, they're still terribly expensive, at about half the price of the 12-inch PowerBook itself. IMO opinion, that's not worth it. For that price, you might as well get a 15-inch PowerBook, which has two slots for cheaper memory.
Personally, I'm waiting for a Rev.B 12-inch PowerBook, which will hopefully be able to get to 1GB RAM without outrageaously priced memory sticks, and will hopefully have a 1Ghz processor and DVI-out as well.
Escher