I have recently joined the world of recruiting (mainly the research side) and have been working (many hours) to get grips on the tools available to identify passive candidates. So far, I've come up with the following list of "Social Networks" to work from:

LinkedIn
Jigsaw
ZoomInfo
Ning
Facebook
Myspace
Bebo
Plaxo
Friendster
Multiply
Windows Live Spaces
Yahoo! 360
Spoke
Ryze
Nexopia
Bright Circles
ERE
Tribe
Jobster
H3
Second Life

WOW! I'm sure there are even more that I don't know about. Some of these may or may not be classified as "Social Networks" and I'm sure each has their pros and cons. Unfortunately, my job requires that I do more than just investigate each site to discover its usefulness.

I'd like to start a discussion to share pros and cons, usefulness, strategies, and experience with any or all (or additional) of the listed tools.

For instance, I read the recent LinkedIn "Rant" and picked up on some of the methods of use. Sounds like (unless you're a corporate recruiter :) building your network is the number one most important task. From there, searching within your network becomes growingly effective. Using InMail and Introductions appears to be more of a recruiting tool than sourcing as the response time of each potential candidate is up to them. Because I am trying to turnaround names and contact info in a short period of time, I think my method will be to find the qualified (as far as I can tell) candidates within my network and use other tools (including the telephone) to zero in on contact info.

Suggestions, criticism, ideas, direction.... all are welcome.