Here are a few resources that have either taught me something or kept me entertained:

Forums

Ask DamageX - I've never really spoken with Damage X, but he seems like a rather insightful guy. Keep your eyes peeled for posts by the late jayeff, too, as he was quite knowlegeable. Lots of good tips, cheater exposure, etc here.

Adult Webmaster Info - Another very good forum with lots of insight into running several different types of adult sites.

Adult Webmaster World - Similar to AWI, this site contains helpful information and experienced posters.

GFY.com - This forum has become more entertainment than insight, and although it is frequented by some of the bigger names in the industry, most of the posts are either drama or mindless dribble. Every once in a while great posts are made, but they're becoming less frequent. It is the most popular forum, but sadly, the slowest and least well-moderated.

Resource Sites

CozyFrog - Contains resources from every corner of the adult market - links to adult affiliate programs, traffic brokers, tutorials, other resource sites, toplists, etc. One of the first resource sites I ever visited.

Cozy Academy - This site was started after Cozy Frog and is actually more useful for newbies in the biz. Some of the articles are a bit dated, but insightful, nonetheless.

Klixxx - Good site that I don't frequent much anymore, but as I recall, it has some very useful articles posted on it - definitely worth checking out.

YNOT.com - I actually hear great things about this site, but to be honest, don't visit it much. They do have quite a few articles and it is one of the larger adult webmaster resource sites around.

XBiz.com - More of an industry news site, rather than resources, but it depends on how you look at it, I guess. These guys usually keep up with the issues that face the industry at a decent pace, so if you're to stay up to speed, give them a visit.

Other Useful Sites

Cheater Hell - A good site to find out who's on the up & up. Check your trades here.

Jay's Trades - Good place to find hardlink trade partners.

Thunder-ball - Also a good place to find hardlink trade partners.

Protect-X - Good place to find traffic trade partners.