OK - a client of mine wants to offload his adult site. It doesn't really make any money, but it attracts a couple of million visitors a year. It is mostly links, etc.

Is this worth anything, and where should I direct them to sell it?

Cheers.

To be honest it isn't worth much with the details you've given. A couple million visitors a year isn't too bad but there are many other adult sites getting much more than that. Because it's just mainly links too, i.e. not much content, that's a problem. If the revenue from it is low, that's the biggest problem, monthly revenue is a selling point if it's really high.