These are instances run by organizations, usually having registration limited to organization members:
- media.libreplanet.org -- The Free Software Foundation's photos and videos from talks and conferences.
- media.freesoftware.org -- Free Software Melbourne's archive of photos, audio and video from meet-up talks and Software Freedom Day presentations.
Also, these sites are running MediaGoblin, but are for more limited audiences (family/friends of person who's running it, etc):
- art.dressupgeekout.com -- Artwork by Charlotte Koch
- isengaara.de -- IsengaaraP's mediahub for sharing eCantorix songs and コスプレ photos.
You can add your instance here, too!