Just when I think I'm current, Google releases a new tool. This is really more of a merging of tools: they now have something called Google Docs & Spreadsheets , where you can log in and find both their web word processing app and their spreadsheet app. And once you've created a user login, you'll find all of your files saved there, too. I posted about Writely  a while back: Writely is now Google Docs.
Come on Google, let's just get it over with: release the presentation software already! You know you want to!