After mentioning them, I couldn't resist a quick look at Google Base and Ning. A search for semantic web at GB reveals loads of books I hadn't even heard of (the bestprices.com links on them seem to be broken, but there's enough info in place to track them down).
Ning looks like it's come on a fair bit since I last looked. Ok, I confess, prurient curiosity got the better of me when I saw " Girl on Girl" listed as one of the apps. Basically it's KittenWar with actresses (i.e. nowhere near as cute). But what's impressive are the hooks they've got into other data - check the biography page for Robin Strasser, who is the current losingest kitten.[Danny]