List of Known Mastodon instances

There is also a list at instances.mastodon.xyz showing realtime information about instances.

Name	Theme/Notes, if applicable	Open Registrations	IPv6
mastodon.social	Flagship, quick updates	Yes	No
awoo.space	Intentionally moderated, only federates with mastodon.social	Yes	No
social.tchncs.de	N/A	Yes	No
animalliberation.social	Animal Rights	Yes	No
socially.constructed.space	Single user	No	No
epiktistes.com	N/A	Yes	No
gay.crime.team	the place for doin' gay crime online (please don't actually do crime here)	Yes	No
icosahedron.website	Icosahedron-themed (well, visually), open registration.	Yes	No
memetastic.space	Memes	Yes	No
social.diskseven.com	Single user	No	No (DNS entry but no response)
social.gestaltzerfall.net	Single user	No	No
mastodon.xyz	N/A	Yes	Yes
social.targaryen.house	N/A	Yes	No
social.mashek.net	Themed and customised for Mashekstein Labs community. Selectively federates.	Yes	No
masto.themimitoof.fr	N/A	Yes	Yes

Let me know if you start running one so I can add it to the list! (Alternatively, add it yourself as a pull request).