I think it would be great if there were screencast demonstrations and code reviews. Members would submit their topics or sample developed widgets and would then present their application to the community. It would include a webinar-style presentation including: screencast, audio, video, source code download, and a link to download the widget.
The widget would be anything from a great one-off snippet of code, a web part/app, application or anything cool that might benefit others. We could even rate the content with stars and “likes” to give feedback as well as a discussion board dedicated to each demonstration.
Members would create something functional and then walk through the steps of how they created it and any troubleshooting they did to get it to work. It may also include business use case briefs to describe the purpose of the solution. I would not be reinventing CodePlex, but rather, a tutorial or instructional demonstration. It would also allow for community feedback and interaction.