You can now export a Google Presentation to the PowerPoint (.ppt) file format.

Editions impacted:
Standard, Premier, Education, Team and Partner Editions

Languages impacted:
US English

How to access what's new:
Sign in to Google Docs, open a presentation and choose "Save as PPT" from the "File" menu.

For more information:
http://www.google.com/a/help/intl/en/users/dands.html