Microsoft's Popfly mashup builder is now in open beta program. During an interview at the Web 2.0 Summit, Steve Ballmer made the announcement and it was demoed for the crowd. Popfly is a Silverlight-based Web browser plug-in that allows users to develop mashups--such as creating an album Facebook friend photos or a simple game--without writing code. It's a slick tool, and along with Yahoo Pipes and Google Mashup Editor is pioneering do-it-yourself programming for mere mortals.
Nutritional Facts (from Microsoft)