I recently found out about yet another "social network", with a difference. For all the readers of this blog who might be graduate students or post docs, here's a new resource for you.
The graduate junction is a networking resource for early stage researchers, who might be doing their masters, Ph.D. or post doctoral research work in Mount Doom (or whatever else you call your research group). It seems to be a nice, focused resource, with sharing of resources,a good discussion forum, indexing by category of your research, a database of conferences around the world, useful resources (particularly useful writing resources), some fun (a crossword), and much more.
If you are a young researcher still working on your thesis or a postdoctoral fellowship, you might find this useful. It is still work in evolution, but I think it does serve a specific need, and there aren't too many resources for young researchers out there. So go check it out.