Google Wave seems to be the new "must have" thing on the Internet judging by the buzz on sites like Lifehacker. Gamers are already thinking about how to use it in online games. So far, most people I've seen using it for RPGs are using it like a chat room and not taking much planned advantage of its special features.
Will Hindmarch had a interesting article on using Google Wave for gaming on his gameplaywright blog. Although his blog is aimed more at Story Games than pure RPGs, his ideas for using Google Wave in gaming are quite adaptable and very much worth a look: Playing On A Wave.