AudienceScience

Formerly RevenueScience, AudienceScience is an online behavioral advertising (OBA) targeting specialist for both advertisers and publishers. Its "AudienceScience Targeting Marketplace" currently consists of 10,000-odd sites.

From the website:

Behavioral Targeting Solution for Advertisers - Be empowered by the first solution to provide you with powerful tools to gain insight into your audience and tailor messages to them on and off your website. This solution enables you to gain insight into your prospects and immediately act on the data, discovering and then targeting your audience with the right message at the right time and place.

As an advertiser you may have access to a wealth of user data online, yet be in need of a simple, scalable, flexible and secure way to collect, organize and utilize that data. This solution leverages AudienceScience's behavioral engine to organize your data into sophisticated consumer behavior profiles, then utilizes these profiles to deliver relevant messaging on your website or across the AudienceScience Targeting Marketplace

For publishers:

The AudienceScience platform features optimal control for publishers as well as numerous targeting and optimization capabilities. We enable publishers to choose how they work with us, with customizable solutions to fit your needs. As a publisher, you can take advantage of our AudienceScience Targeting Marketplace™

[Options include:]
On-Site Behavioral Targeting
Inventory Extension
Behavior Syndication
Inventory Provider

Definitely worth a visit. It's not entirely clear what the publisher requirements are, but my guess is they're rather stringent. Only well-established sites need apply.

Visit AudienceScience