Are you in any of the groups on those sites? There are tons of them and with the new forum and chat features the ability to socialize is pretty nice. On dA if you're a nature lover, have a d60 and take a lot of pics of bugs, that's three potential clubs you can join. Flickr is the same, as far as socializing those are both pretty great.
For advanced critiques from a mostly older crowd, I have to say I'm really enjoying photosig.com dA and flickr are both really great though, I'm part of 3 clubs on dA. Nikon, nature and landscapes.
