I try to keep you up-to-date about the newest useful community sites that are dedicated to physicians and/or scientists.  Now let me share Academia.edu with you, a social network with a nice concept:

It displays academics around the world in a tree format, according to what university/department they are affiliated with.

It enables an academic to have an easy-to-maintain academic webpage. A sample page on Academia.edu is here: RichardPrice

Researchers don’t have enough time to construct web pages for themselves (where to host it, how to design it) so Academia.edu helps them how to do that. Good idea, great implementation.