What about something like Website reviews - I know this could open a can of worms regarding advertising, but owners could mention their site and other members give them advice on design, SEO etc.
I have been meaning to introduce that, and I thought one way to stop people just tossing in their site and then disappearing again would be to say that only active posters can submit a site for review - say 10 posts minimum. That's what they do on the High Rankings forum, but there it's 20 posts. (Not so easy when you don't have anything to add to their knowledge base!)
The thing that has stopped me from doing it is how time-consuming a site review can be. I've done a fair few by email and it takes more than a few minutes.
But I'll add it, because it's a good idea, and there'll be more than just me giving an opinion.