I guess many of you have heard about Letterboxd. To me it's THE social network about movies - a place to log what you see, give your ratings, keep watchlists and other lists, see what your friends are watching/liking. To me it seemed different from the others mostly in how nice the UI looks and feels compared to other similar services. And especially the way movies are shown with posters makes a lot of sense to me.
Anyway, at the moment I just noticed there is a campaign to let you import data (in IMDb format) into Letterboxd for free - usually you would have to pay for the Pro account to be able to do that. So at the moment there's a rather good opportunity to give Letterboxd a try if you have a lot of movie watching data or ratings on some other service.
BTW, I'm T4ffer on Letterboxd.