Other Databases Relationship Type/Whitelist
Rate Your Music (http://rateyourmusic.com/)
Merge MusicMoz here (it's had about 30 uses in the last year, and we have very few uses of it in total too - around 1300 for a generalistic db is laughable, we added the SoundCloud relationship a few months ago and it already has more uses)
WorldCat (http://www.worldcat.org/): International network of library holdings; can include tracklists, track lengths, labels, catalog numbers, credits and ISBNs (which can be translated into bar codes)
Musik-Sammler (http://www.musik-sammler.de/): German database, tends to have stuff that is not on Discogs and the like
Discografia Nazionale della canzone italiana (http://discografia.dds.it/): Italian database, especially useful for older releases, includes tracklists, labels, cat#s, credits and sometimes cover art
ESTER (http://www.elnet.ee/ester/): Estonian library database; fairly complete, often including cat#s, full tracklists and even writing and performance credits - of course it's fairly niche, but hey, so is other stuff
Encyclopedisque (http://www.encyclopedisque.fr/): French vinyl stuff - we already have permission for using their cover art, but since we're moving cover art stuff to the CAA, it'd be nice to have a more "legit" way of linking to them
Discos do Brasil (http://www.discosdobrasil.com.br/): Brazilian music database based on the creator's private collection. Not publicly editable, but contains over 6000 Brazilian releases with detailed credits. (example)
rolldabeats (http://www.rolldabeats.com/): thousands of "dance music" (dnb etc) releases, including a decent amount of white labels.
psydb (http://www.psydb.net/): 8924 psytrance releases, with label/cat#/tracklist info. however no updates since 2009
Metal-Archives (http://www.metal-archives.com/): the place to find obscure demos from Montenegrin black metal bands (literally: http://www.metal-archives.com/albums/Zaimus/Demo_2007/251573 ) It is by far the most complete metal database. A release page is more like a release group, with the original release in it, and other releases details in the annotation.
Guts of Darkness (http://www.gutsofdarkness.com/) is similar but less complete, however it is interesting for artists not considered as metal by M-A.
Merge IBDb (284 uses in total) and IOBDb (17 uses in total) into this (for some comparison: conductor position was added yesterday and has been used 180 times).
Theatricalia (http://theatricalia.com/): they have some MB links and someone asked if we could link to them http://wiki.musicbrainz.org/Talk:Proposals/History#Theatricalia - can anyone familiar with this kind of stuff tell me if the content is any good and it makes sense to link? Their stuff is under CC database licenses http://theatricalia.com/about
OCRemix (http://ocremix.org/): games music - not only their own stuff, which is already a lot: they also have "work" pages for videogame music, and even chiptunes for some of them (http://ocremix.org/song/1022)
http://www.45cat.com/ -- dedicated to 7"/45s only. Very clean, extensive and reliable site.