In addition to desktop office applications, we have Web 2.0 online spreadsheets services as well as online word processors like Writely, gOFFICE and Thinkfree. What is clearly missing from the online suite of Web 2.0 Office Suites is an online PowerPoint service.
Now we have Thumbstacks!. It allows you to create web based PowerPoint presentations. It all runs in your web browser. You can create your presentation, save it, modify it, update it, whatever - then click publish and you will get a link you can use to share it with everyone.

Pretty cool service. Like Num Sum had the first mover advantage for online excel spreadsheets,
Thumbstacks! has the advantage for online PowerPoint presentations