In my experience, by far the best resource for downloading AV (mostly Japanese) was the "BT Centre for Adult" forum section of ck101:
http://ck101.com/
It's all in Chinese, but Google Translate is your friend and it's pretty easy to navigate otherwise. You may have to get registered to see torrent links, but no posting is required. There's an absolute ridiculous number of DVDs being uploaded on there on a daily basis with sample/cover pictures so you don't spend all day downloading something that isn't your cup of tea.
For those that aren't familiar with BT, it's a file sharing program called BitTorrent. I personally use the uTorrent client, but to each their own. If you're new to BT, just keep in mind that it'll hog up bandwidth if you don't set things properly or remember to stop the program manually.
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Last edited by barg123 at 21-12-2010 22:09 ]