When visiting the CodePlex site, click on the Project Openings link.
This will direct you to a listing of projects with openings sorted with the most recent openings first.
Project openings can be tagged with specific keywords by the project coordinators. You can utilize the tags specified to refine your search results by clicking them in the “Refine results by” sidebar.
When you find a project you would like to join click on the “Join this Project” link. This will direct you to the homepage of the project with the request dialog open and ready for your submission.