Social Networking Tools:

Delicious: http://delicious.com/
Getting Started with Delicious: http://www.youtube.com/watch?v=NGXElviSRXM
Get Started Assistance: http://delicious.com/help/getStarted

Diigo

Diigo: http://www.diigo.com/
Diigo Tutorial: http://www.slideshare.net/cliotech/diigo-tutorial-presentation
Diigo Highlight and Share: http://www.youtube.com/watch?v=0RvAkTuL02A

Twiducate

Twiducate: http://www.twiducate.com/

Social networks:
Nice Net: http://www.nicenet.org
Ning: http://www.ning.com
Twitter: www.twitter.com, communication tool