LinkEX

The obligatory linkback is very softcore by my standards, but still probably not appropriate for a mainstream site. Do
you have a mainstream option? If not, you should consider including one. On the other hand, there might be so few
mainstream sites using this that it wouldn't be worth the effort. Those people think much differently about generating
traffic than we adult webmasters do.

In my experience linkex seems to be for adult sites. If you put it on any other site
you would probably spend all your time removing porn links no matter what type of
rules you post, no one reads them. (I'm not the author of linkex)