If you want quick overviews of each of the real popular networks you can get them here:
http://www.publisheraid.com/revenue.html
For example:
Fastclick -- Quick Info
Ad Formats: Full Banner, Leaderboard, Invue, Interstitial, Half Page Ad, Text Ads, Skyscraper, Wide Skyscraper, Rectangle, Medium Rectangle, & Pop-Under
Ad Methods: CPM & CPC
Targeted Ads: Never
Interface Usability: Above Average
Referral Program: Yes (5%) - Not Permanent
Commission Taken: 35%
Payment Terms: 20th of the month
Traffic Required: 3,000+ Page Views Per Month
Similiar To: Tribal Fusion, Burst Media!, & Casale Media
There are two extremely detailed reviews of Casale Media and InterClick there as well.