Broadcast Co-Op and Vendor Support Programs can provide stations with a wonderful competitive advantage as they reach untapped potential advertisers. An online service that is worth exploring is The Co-Op Advertising Program. Note: while their online service appears to be updated regularly, the printed book advertised is very dated.
Another excellent source of information is Multiad. They have a large library of updated programs and support designed to make initial sales and the follow-up process less painful.