To be honest with you it all depends on what product you are wanting to advertise.
No point in advertising a fetish product on a site that has a small base of fetish webmasters etc.
I would suggest going to google and doing some searches for resources based on your product and then, take a look through those sites and see what they offer in exchange.
For example, if you have a content company, you might do a search on 'adult content providers' or, 'content providers', 'adult content' etc.
If you were going to be advertising something related to traffic, you might like to do a search on 'adult traffic sources' 'adult traffic resources' etc etc.
If you are marketing something to the international webmasters a search for 'foreign resources', 'international adult webmasters' etc should yield some good results.
In general, a lot of resources get a lot of traffic however, the more highly targeted that traffic is for YOU the better your ad results will be overall.
Feel free to shoot an email over to
[email protected] for some more assistance on choosing the right place to advertise your products, services.