For this program i would check out this client list and ask a few questions, but for Adserving i would stick with the known companies.
Think about this, when a major advertiser want to display ads, they are going to go with a large player so they get all their reports and cost in one nice package. They do not play with smaller players, so most likely the company has a couple of smaller advertisers but most of their campaigns are resold or ruminant campaigns.
I would take a look at these well known providers for quality campaigns, but also be used as an adserver. These two companies have tool for the AM to see all campaigns, payout and performance numbers and lets you select who you want or not want to run on your site.
I know a couple of people at these companies and if you like i can give you an introduction. Just put together a One-Sheeter (site demographics, traffic, channels and size) and they will give you their rates, fees and tool listings. it is quite simple.
You can also take a look at Doubleclick, 24/7 Real Media or Bluestreak.
Let me know if you have any questions or need to know what to ask for when approaching them.