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They aggregate news from major sources and categorize them.

From their homepage:
Congoo is a free real-time news, networking and information portal. Ongoo's unique channels merge the most important news with industries' most important people.

One of the larger ad networks but runs media only on a CPM basis. They are an ad exchange, so they purchase media from other networks.

Includes aol.com and the AOL client.

An ad network with 3,500 sites. They have the following targeting capabilities:

• Behavioral targeting - user behaviors are captured on 70 partner sites and then targeted on their network.
• Creative retargeting - allows you to pixel your banners and retarget people you're already hitting on another site
• Leadback targeting
• Custom behavioral segment targeting - they can target based on SIC Code, Domain and Fortune 500 rank. The minimum spend is $50k.

Ad Network with 155MM monthly uniques offering the following targeting types:

• Behavioral/Demographic - called Targeted Spectrum
• Leadback targeting - called Encore

Permission Data is a CPA vendor.

The biggest ad network in the world, which also includes AOL. Like other large ad networks, they can run media on a CPM, CPC or CPA but since it all runs on the same network, if you do a performance deal with them, volume can fluctuate significantly.