Footprints For Ad Networks

I need to check a huge list of sites to see if they support any ad networks. Obviously the majority will be Google Adwords but I am interested in others too. What I don't know how to do is find websites that use these networks so I can find a footprint to search for in my huge list of sites. Does anyone know a good way to go about that or know of any ad networks and their footprints? Some networks I'm interested in are:

Adwords
Footprints:
- "Ads by google"
- "google_ad_client"

AdCenter by Microsoft
Yahoo's Ad Network
Pointroll
AdBrite
Clicksor
AdOnion

Thanks

compete.com might be useful, you have to pay like $90 a month for their service though.

Thanks for the response.

I am slightly familiar with compete but I'm unsure how they(their services I know about anyway) could help me with what I'm looking for. Either way the monthly payment is out of the question and if their's a trial period I'm sure it's been used.