Freelance journalists tend to join communities.
Although it is not specifically used for freelance, there is a group where advice is given and people discuss freelance. There is also a free monthly training session.
Freelance workers can post their work to either their own personal Facebook, or pages on Facebook that are specifically made for freelance journalists to share their own and discuss with others their work. There is a site which is very much like Facebook, but is made for journalists.