There's no sense in signing up for these sites unless you have friends on them who can recommend and share movies.
Post your username and site you use and I will update the first post.
iCheckmovies.com
http://www.icheckmovies.com/profiles/Dukefrukem/
http://www.icheckmovies.com/profiles/elixir/
http://www.icheckmovies.com/profiles/antoine/ (Isaac)
http://www.icheckmovies.com/profiles/gizmo_ber/ (gizmo)
http://www.icheckmovies.com/profiles/Yxklyx/
letterboxd.com
http://letterboxd.com/angrycinephile/
http://letterboxd.com/artboiled/ (nunber8)
http://letterboxd.com/cinelixir/ (elixer)
http://letterboxd.com/davidseven/
http://letterboxd.com/dukefrukem/
http://letterboxd.com/Ivan_Drago/
http://letterboxd.com/thequestyen/ (EyesWideOpen)
http://letterboxd.com/rowland/
https://letterboxd.com/Skitch
http://letterboxd.com/plashy/ (ThePlashyBubbler)
http://letterboxd.com/transmogrifier/
http://letterboxd.com/Thirdmango
http://letterboxd.com/filmadept/ (Fezzik)
http://letterboxd.com/dsmith724/ (Derek)
http://letterboxd.com/lilyho/ (Li Lili)
http://letterboxd.com/gizmo/
http://letterboxd.com/jwier85 (ledfloyd)
http://letterboxd.com/elstongunn59/ (Kurosawa Fan)
mubi.com
http://mubi.com/users/5025304 (Dukefrukem)
http://mubi.com/users/975172 (elixer)
http://mubi.com/users/121436 (Kurious Jorge v3.1 )
Criticker.com
http://www.criticker.com/profile/Dukefrukem
http://www.criticker.com/profile/zachheltzel (eternity)
http://www.criticker.com/profile/RetinaScan (Lazlo)
http://www.criticker.com/profile/Gizmo
http://www.criticker.com/profile/Skitchima (Skitch)
http://www.criticker.com/profile/Spinal
http://www.criticker.com/profile/Raiders
http://www.criticker.com/profile/megladon8
http://www.criticker.com/profile/iosos (Sven)
http://www.criticker.com/profile/bialas (Ezee E)
http://www.criticker.com/profile/B_Side
http://www.criticker.com/profile/Watashi
http://www.criticker.com/profile/soitgoes
http://www.criticker.com/profile/madman
http://www.criticker.com/profile/Antoine (Isaac)
http://www.criticker.com/profile/grouchy
http://www.criticker.com/profile/barty
http://www.criticker.com/profile/evilshoe
http://www.criticker.com/profile/ears550/ (elixer)
http://www.criticker.com/profile/monolith94
I also have three invites to Letterboxed if anyone wants then. First three that ask in this thread gets em.
Mubi is least favorite site so far. Feels too pressured to pay for a subscription. iCheckmovies is getting there too, but the official lists are valuable.