Ingenio will begin providing pay-per-call ads on AOL's search results pages this week, reports MediaPost. The listings will appear at the very top of AOL's search results page, above other sponsored listings - provided by Google - and the organic results. The minimum bid for a listing is $2 per call; many categories are going for more than $20 per call.

The pay-per-call model is similarly to that of sponsored links, but advertisers bid on categories of business, not keywords.

Some of the hotly contested categories include finance and real estate, automotive, health, and various home-improvement trades.