Reddit is more aimed toward generic porn when you look at the highest subscribed X-rated places, but some subreddits do get through that are special interest. The one we're talking about here is BDSWGW - I know that's quite a mouthful, but it's just a simple combination of BDSM (which means bondage, domination, pain) and 'gone wild', which is a phrase produced by the reddit community to mean pornographic or sexual in nature.
/r/BDSMGW has 33,000 subscribers and a number of similar subs that are based on a varied number of fetishes and engagements. There's little restriction on the content, with the availability for blood play to also be included. It seems as if the moderators of the site have a pretty lax approach to controlling the flow of content - they typically just allow the user base to decide what's good based on the number of upvotes and downvotes posts receive.
Anyway, I think I've said enough, and truth be told, the best part about BDSM GW is the fact that all of the content is amateur in nature and uploaded by members of the community. I wonder one thing! How famous fetish content became after 50 Shades Of Grey?