I think AOL calls this service "Custom Interactive Areas." I guess they do that because the keyword doesn't just take them to your site, but leaves them in a AOLified version of your site. I don't know if you've used AOL or not, so I don't know how much you know about their keyword system. I bet it's not cheap. Anyways, there's only one way to find out; visit: http://mediaspace.aol.com/product09.html
Hope this has helped. If you want anymore help, just ask.