Below is a list of media buying advertiser networks. If you are looking for places to buy huge traffic to promote CPA offers, this is the right list for you.
http://www.advertising.com/
http://www.valueclickmedia.com/
http://www.casalemedia.com/
http://www.tribalfusion.com/
http://www.adbrite.com/
http://www.cpxinteractive.com/
http://www.247realmedia.com
http://www.adtegrity.com/
http://www.realtechnetwork.com/
http://www.vizi-inc.com/
http://www.drivepm.com/
http://www.bluelithium.com/
http://www.venturedirect.com/
http://www.valueclick.com/
http://www.undertone-inc.com/
http://www.topica.com/
http://www.theblindnetwork.com/
http://www.bluestreak.com/
http://www.silvercarrot.com/
http://www.revenue.net/
http://www.amperemedia.com/
http://www.revenuescience.com/
http://www.adteractive.com/
http://www.prospectiv.com/
http://www.adknowledge.com/
http://www.euroclick.com/
http://www.offerfusion.com/
http://www.dedicatedmedia.com/
http://www.specificmedia.com/
http://www.clicksor.com/
http://www.claria.com/
http://www.industrybrains.com/
http://www.addynamix.com/
http://www.motiveinteractive.com/
http://www.adpepper.com
http://www.coverclicks.com/
http://www.vendaremedia.com/
http://www.mediawhiz.com/
http://www.burstmedia.com