The Internet really kicked off after 4chan when it came to the whole image board way of content sharing - iChan.net aka iChan.org is one such clone site that has a heap of boards devoted to various topics. You've got your standard places such as Tech and Random but also NSFW focuses with boards dedicated to camgirls, fetish porn and transsexuals. Oh, there's also a metric buttload of hentai content too, with boards for furry, yaoi, yuri and ecchi action. I don't think I've seen a chan board so devoted to Hentai, actually, which is quite surprising.
Some of the boards are a little dead, but I suppose if no one visits them because they can't find new content, no one would bother sharing. Seems like a vicious circle with no end if you ask me. Anyway, yeah - iChan is pretty much all about the Hentai with some random porn chucked in, so if you want that kinda fun, head on over to get it.