This is something I encourage people to do. It's additional exposure for the radio commercial - possibly for the station, too - and it helps make a client's site more "sticky." Most recently, I've urged a political candidate I'm consulting to do this. At worst, it can't hurt. Here's an article I ran across today, where the writer mentions an auto body and paint shop that posts their radio ads to their website. Anyone else doing this regularly?
Rod,
We're stiill trying to convince our advertisers that it is a good idea to have websites that are more than online signs. Our website has banner ads with links, and we offer the opportunity to upload sponsor ads, and podcasting. So far both of the latter are being received with overwhelming apathy.