SDN -- A collection of well meaning students offering advice on how to succeed at your dental education. Throw in a few dentists who for once get to be the people with the answers instead of questions and you've got a great resource on surviving dental school. The fact that y'all think of this stuff outside the ivory towers puts you in the top 20%.
Dental Town -- Take 35,000 dentists, lab techs, hygienists, salesmen, and their mothers and let them talk about ANYTHING. It's a great place for moral support, clinical tips, jokes, and a sense of community.
GenR8TNext -- The world's greatest dentists (and they're not afraid to tell you they are) discussing high dollar dentistry.
RxRoots -- A collection of premier endodontists discussing the subtleties of root canal therapy. If you want to do endo, you owe it to yourself and patients to check this forum out.
JMHO
Rob