A great number of individuals in the Plone community have graciously created themes for use by other people. The process for distributing these themes is fairly simple. It is important that the quality assurance process described above is followed, especially in terms of documenting dependencies, the installation process, and any content that needs to be created to support a theme.
You should store your theme product in Plone's "collective" SVN repository. To gain access to the repository, visit http://plone.org/documentation/manual/plone-developer-reference/overview/contributing. You can also find information on the Subversion commands you will need at http://plone.org/documentation/how-to/svn-import-to-plone-collective-unix/. Also, you should upload release versions of your theme product to the Python Package Index, PyPI. See the instructions at http://pypi.python.org/pypi for more information.
Then, you'll need to add your product to http://www.plone.org...