CodePlex is Microsoft’s open source project hosting web site. You can use CodePlex to create new projects to share with the world, join others who have already started their own projects, or use the applications on this site and provide feedback.
From their FAQ,
What are the requirements for hosting a project on CodePlex?
Your project must meet the following criteria:
- You must choose a license for your project (license resources: Open Source License page on Wikipedia)
- It must be an ongoing project (no “abandoned” projects)
- It must have source code (no non-software projects)