The newsgroup uk.media.dvd is a good place to sell/trade any mainstream or adult DVD's. I have sold a few of my adult titles using this NG without problem as long as they are reasonably priced.
Some people are asking silly money for used disks when you can import them cheaper. Advertising a high price tends to attract a few choice remarks from the regular posters.
Just becareful of sending your goods away before receiving payment. I only sell my DVD's and do not trade them and have not encountered any bad experiences yet. But there have been cases of traders being scammed.
I thought about using an auction site previously but it was easier just to post it on the NG.
Good luck.
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