Unlike Yahoo Pipes, Popfly is not aimed at tech-savvy users. Microsoft is hoping to attract non-professional programmers and hobbyists who are interested in building mash-ups, gadgets, simple Web pages and basic applications.
Popfly Blocks -- 40 of which are currently available -- will allow users to snap together existing Web pages, data and syndicated information. Microsoft and third-party developers are building more custom blocks.
The Popfly design surface is where users can drag, drop and connect their blocks to build mash-ups and applications.
Popfly users can embed their own or others' customized mash-ups, gadgets and applets into existing Web sites.
Popfly also includes the Office Live Web designer for users who want to visually design Web pages without having to write code.
More Web 2.0 functionality in Popfly: Users can rate and rip projects, save them as Vista sidebar gadgets and/or integrate them directly into TypePad, Windows Live Spaces and other blogging platforms.
To make Popfly more interesting to the "MySpace generation," Microsoft is adding in social-networking capabilities, allowing Popfly users to create their own Popfly communities.
Also in alpha is a new Visual Studio Express Popfly Explorer plug-in, allowing users to upload and share their mash-ups with others.