The mentioned open-source project sites ares still good. The SourceForge and CodePlex were there for many years, and they are still functional. Some of Git’s predecessors, such as CVS and Subversion, have a central “repository” of all the files associated with a project. The SourceForge and CodePlex, code-sharing sites are using central repository pattern.
However, Git is different. It is build on a distributed version control system design. As it is also mentioned on Git's official website:
It outclasses SCM tools like Subversion, CVS, Perforce, and ClearCase with features like cheap local branching, convenient staging areas, and multiple workflows.
In recent years there is a trend to migrate open-source projects to GITHub. Thus, it is becoming the next HOT Spot for open-source community to share their goodies.
In summary, you may get more attention and more projects needing contributors to help.