Kontera is one of the leaders in PPC Intext Advertisement Providers. They have a wide range of Advertisers and accept almost all kind of sites.
What it normally does is to find the keywords in your content and automatically turns it in a link. When visitor hovers his mouse over that link, he/she will will be shown the ads.

Heres the few details about them

What are ContentLinks?
ContentLinks are contextually relevant keywords discovered in real time on a publisher’s web page that are automatically turned into a link to the most relevant and highest paying text ad from one of Kontera’s thousands of advertisers.
What ContentLink can do for you?
Kontera’s ContentLink In-Text Advertising solution lets you monetize your content in real-time, enabling an incremental increase in ad revenue by providing a new source of untapped ad inventory that does not compete with the other ad programs running on the site. ContentLink™ also creates a valuable user experience by serving relevant and informational ads that match the user’s interest and frame of mind.
The ContentLink advantage:
At the core of Kontera’s patent-pending technology are a set of proprietary algorithms that enable publishers to maximize their revenue and earn higher Click Through Rates. Statistical text analysis and clustering methodologies are used, combined with semantic analysis procedures that utilize a proprietary taxonomy of subjects, keywords, and unique relationships between them. Kontera’s platform, optimized and proven on thousands of web pages over the last seven years, facilitates the analysis of each web page in real-time. Keywords and topics are then extracted and ranked, and then instantly matching to the advertiser’s most relevant text ad. The greater relevancy between the content, keyword and text ad made possible by Kontera’s proven technology increase the publisher’s revenue.