Empressr, headquartered in New York, is the newest entrant into this space. It’s a flash-based application with rudimentary features.
Online office applications are serious business with real acquisition possibilities. Writely, an online word processor, was acquired by Google earlier this year, and Google launched Google Spreadsheets, an online version of Excel, last month. Powerpoint web applications are probably next.
There are three key feature areas that I think must be covered if an online version of Powerpoint is to succeed. First, at least basic creation tools need to be developed. Second, the applications need to import and export in Powerpoint format. Third, the files need to be viewable online via shared or public hyperlinks. A PDF export feature would be nice as well.
Empressr allows sharing of presentations, but the creation tools aren’t there yet and there is no import/export to powerpoint (or PDF) available. Look for future versions to include these features.