Social Network Basics
Social Networking Basics
Social Networking Guide for Beginners - A Social Networking Help Guide
The Top Social Networking Sites
Introduction: Blogging and Social Networking Basics for Professionals

Social Network Sites
Twitter: What are you doing? 
Welcome to Facebook! | Facebook
Welcome to Flickr - Photo Sharing
Flixster http://www.flixster.com

Feeds
Twitter / jencius
Facebook | Marty Jencius
Flickr: Jencius' Photostream