Here is a website I've found whose porn producers are looking for affiliates: http://affiliates.eroticy.com/pressRelease.asp?release=22

Starting your own porn business may not be as easy as it looks. With the high number of porn sites (smut glut) and, thus great competition, it definitely takes hard work to attract visitors to your sites.  Online porn giants rely on ma-and-pa operations to feed traffic to their sites through a web of banner ads and affiliation programs. However, the problem with this is that these business pay our more in the affiliate programs for traffic than they make in one membership. Now these large businesses are dependent on new sites, constantly to become affiliated with these paid sites and the challenge is that so much content is free nowdays, why should they pay? With an abundant amount of free explicit material, it is difficult to attract subscribers to pay for these sites.