If you are a developer on Codeplex then there are now two Codeplex LinkedIn groups for you to join.
Codeplex Developer
All members must have an account with CodePlex and be a developer on at least one project. Please provide your account name after requesting to join...
Codeplex Coordinator
All members must be a Coordinator of at least one Codeplex project.
NOTE: All requests to join these groups will be checked before they will be approved. Please provide a link to your Codeplex profile.