http://babu.jp/~mbc/ (meta board community)
http://i-bbs.sijex.net/imageBoard.jsp?id=g1830037 (anime guro img board)
http://f27.aaacafe.ne.jp/~ringoki/ (links to a few img boards, sorted by category)
http://www.2d-tenshichan.com/menu.html (pretty shitty hentai img board, but some might like it)