Exhentai is an anime/manga image site which has a lot of hentai images (as the name implies) and content (such as doujin/doujinshi scans from Japanese magazines, CG artwork, hentai manga series, fan art, etc...)
Ranked in these QuestionsQuestion Ranking
Pro Complete doujin library
It has a lot of libraries.
Con Slow server
Image load too slow.
Con Website access is limited
Need exhentai plugin and user account to access.