Google Adwords – http://adwords.google.com
MSN Adcenter - https://adcenter.microsoft.com
Looksmart – LookSmart > Pay-Per-Click Search Advertising
7Search – 7Search | Pay-Per-Click Search Engine Advertising Network
Facebook Ads – Advertising | Facebook
MyAds – http://www.myads.com
Clicksor – Contextual Online Advertising and Behavioral Marketing Company
Marchex - Marchex : Pay Per Click
AdSide – AdSide
Adblade – Adblade - Online Advertising and Monetization Services
Adbrite – adBrite ExchangeAdSonar – http://www.adsonar.com
POF Ads - https://ads.pof.com
Advertise.com – Online Advertising Company : PPC : Email Traffic : Remarketing : Display Advertising : Online Ads : Pay Per Click Advertising : Advertise.com
Pulse360 – Pulse 360 - The Leader in Content Targeted Sponsored Links on the Web's Best Sites
AdClickMedia – AdClickMedia Advertising Network - Pay Per Click Advertising, online text advertising, banner advertising, and Interstitial advertising.
Bidvertiser – BidVertiser - Pay Per Click Advertising On Sites Of Your Choice.
Adknowledge – Adknowledge.com | The leading long tail marketplace
Findit-quick - Pay Per Click | Pay Per Click Advertising | PPC | PPC Advertising | Pay Per Click Search Engine
AdManage – Admanage affiliate and advertising network - PPC, CPC Banner, In Text, Display Ads, CPV, Domain Parking
Findology – http://www.findology.com
AdMarketplace – Performance-Driven Search Advertising | adMarketplace.com
Ezanga - http://www.ezanga.com/
Pay Per View Traffic Sources
Media Traffic – Media Traffic - CPV PPV Contextual Advertising
Trafficvance – Trafficvance :: Advanced Display & Text Link Traffic | Home
DirectCPV – Pay Per View PPV Cost Per View CPV Contextual Online Advertising Network
AdOnNetwork – Pay Per Click Advertising | Pop Under Ads | AdOn Network
Lead Impact – LeadImpact
Pay Per Text Traffic Sources
Infolinks – Pay Per Click Advertising - In Text Ads for Websites by Infolinks
Kontera – Kontera
50onRed – Performance is Paramount | 50 on Red
Vibrant Media – Vibrant - The Leaders of Contextual and In-Text Advertising
Linkworth – LinkWorth | Search Engine Marketing - Text Link Advertising
Inlinks - inLinks - In Content Link Market Place
InText – InTEXT SYSTEMS (wwwserver2)
Media Buy Traffic Sources
Casale Media – Casale Media - Home
Valueclick – http://www.valueclick.comhttp://www....ickformula.com
Tribal Fusion – Home « Tribal Fusion
Traffiq – http://www.trafficq.com
Yahoo AdReady - AdReady - Online Display Advertising Campaign Software for Agencies, Advertisers & Publishers | AdReady
Ask – http://www.ask.com/products/
Illyx - illyx Network | Affiliate platform Pay per install, impression, click
MegaClick - NOTICE
GoTraffic.com – Online traffic marketplace, where website owners and online marketers do business.
Advertising.com – Shopping Search | Ask.com
BuySellAds – Buy Ads | BuySellAds
DoubleClick – DoubleClick: The technology foundation for digital advertising
Burst Media - BURST MEDIA
Dashboard Ad - Dashboard Ad
Adengage - AdEngage - Engaging Internet Advertising
CPX Interactive - Welcome to CPX
Undertone - Undertone
Ad Pepper - ad pepper media: Home
Contextual Pop Ups
Adoori – Adoori - Reinvent Your Advertising.
Infinity ads - Contextual Advertising | Pop Under - Pop Up Ads - Targeted Internet Advertising Services
Retargeting
AdRoll – Retargeting and Display Advertising | AdRoll Retargeting
AdRetargeting – Ad Retargeting - Behavioral Retargeting - Behavioral Marketing - Search Retargeting
Fetchback - FetchBack - The Retargeting Company
Recrue Media - Retargeting Advertising | Retargeting Companies | Recrue Media
Domain Traffic
Elephant Traffic - https://www.elephant-traffic.com
Mobile
Admob – Mobile advertising with AdMob: mobile ads for apps ? Google Ads
Jumptap – Jumptap | The Leader In Targeted Mobile Advertising
inMobi – InMobi | Global Mobile Ad Network
Adfonic – Adfonic
Mojiva – Mobile Advertising with Mojiva's Mobile Ad Network
Mobclix – Mobile Advertising, App Advertising and Analytics, Mobile Ad Exchange, Mobclix
Credits to Gaugher Chaudhry. I got this list when I opt-ined on his blog. It's a great list so it might be a good share for those who are starting.