Each site in the search results on Overture.com is lables with either "sponsored listing" or "additional listing." If you search on Overture for a phrase which has little commercial value to Webmasters, then you will see results labeled "additional listing" which are pulled from the Inktomi database. A good example is this Overture search for clinical neuropsychology.

Some of these additional listings are actually paid listings, but many are not. For more information about Inktomi listings, visit How can I submit my site to the Inktomi database?