The Community Contributions category is a place to share things that you have created that you think will be of use to the QIIME 2 user community. This can include plugins (but also consider sharing those on the QIIME 2 Library, as documented here), reference databases, documentation, workshop content, or other contributions.
You can get a feel for the most popular contributions by viewing this link - as you can see, content shared here can be widely accessed. Some of the most popular posts in this category have been viewed well over 20,000 times.