Live instances

Public

These are public sites running GNU MediaGoblin:

https://gobblin.se (previously mg.wandborg.se) -- Registration open, but uploads are currently not working; all media types enabled (except STL/3D, at the moment) -- details; Joar/mg.wandborg.se.
Your browser may not trust the certificate authority: http://wiki.cacert.org/InclusionStatus.
http://roaming-initiative.com/mediagoblin/ running on http://hyperboria.net/ apparently! reddit thread
http://mediagoblin.com -- Currently registration and video are disabled; you have to ping Chris Webber for an invite.
https://efjz.in -- "EricFontaineJazZmediagoblIN" is for me to archive recordings of music performances of me and my fellow musicians.
http://barn.kerosenecow.net/ -- Registration disabled. This is mainly a showcase for development of the MG-GIMP project (a Mediagoblin plug-in that permits hosting of GIMP images and resources).
https://goblinrefuge.com -- Registration open. Images and video enabled.
https://mediagoblin.pixelminers.net/ -- Registration closed due to registration spam. Hoping to reopen soon. For now you might talk to Reezer for an invite.

Not working?

http://isengaara.de (not running as of 13 Oct 2014) -- IsengaaraP's mediahub for sharing eCantorix songs and コスプレ photos.

These are instances run by organizations, usually having registration limited to organization members:

http://medii.ceata.org -- Fundația Ceata, Romanian Free Software and Free Culture activist organization. Registration is currently disabled.

http://media.libreplanet.org -- Videos of the LibrePlanet 2013 conference (Free Software Foundation). Registration is currently disabled.

http://media.openvideo.pro -- Open Video Productions, L.L.C. Registration is currently disabled.

http://media.chicagolug.org -- Chicago GNU/Linux User Group. Registration is currently disabled.

Also, these sites are running MediaGoblin, but are for more limited audiences (family/friends of person who's running it, etc):

maiki’s baby photo site (can't connect on 16 Oct 2014)
haise family photos (currently with a baby focus)
jpope's instance -- Registration currently disabled.
thelovebug's instance (registration closed)
spaetz' private pics (under construction on 16 Oct 2014) Sebastian Spaeth's pictures, family and stuff (registration closed)
gallery.Dick-Thomas.co.uk (can't connect on 16 Oct 2014) Dick Thomas' pictures, family and stuff (registration closed)
media.wigunnara.com (can't connect on 16 Oct 2014) Giri Alam's pictures, family and stuff (registration closed)
photos.katsarov.org Photos by Anton Katsarov (registration closed)
media.micha.elmueller.net Photos by Michael Müller, all licensed under CC-BY (registration closed)
photos.technicallyandrew.com (error 503 on 16 Oct 2014) Photos by Andrew Browning (registration closed)
noreal.info/galeria (does not open on 16 Oct 2014) Run in a Raspberry-pi by Arder Vegan (registration closed)
ardervegan.info/media (error 404 on 16 Oct 2014) Run in a Raspberry-pi by Arder Vegan (registration closed)
mediagoblin.aurka.com janssen’s personal mediagoblin-instance with concerts, demonstrations and other stuff (registration closed)
[1] (can't connect on 16 Oct 2014) Pictures and music from Charles Pehlivanian, hosted on a Raspberry Pi.
media.deadsuperhero.com Artwork and photos from Sean Tilley, who writes MediaGoblin themes for fun.
media.chrishancockart.com Artwork from Chris Hancock. (registration closed)

Indyshop:Fashion Blog & Independent Shop Showcase - Registration by email request for independent brick and mortar shops only.

You can add your instance here, too!