Save as html. The help says that this is an option (twice), but I don't see it in the save-as or any other menu:
Microsoft PowerPoint 2010 offers you a range of file types that you can save as, such as JPEGs (.jpg), Portable Document Format files (.pdf), web pages (.html), OpenDocument Presentation (.odp), and even as a video or movie (and more).
You can also open various different file formats with PowerPoint 2010, such as OpenDocument Presentations, web pages, and other file types.