While I don't have banners for a competing host on our site, if users are looking for a windows platform or something that we do not offer, we give the recommendations of places that we have used ourselves. Same with users that want to operate a shared SSL for hosting. We have a competing host for the same product that we sell and we send the clients to them.
Over the years the two hosting companies have traded customers back and forth a number of times. The relationship works out pretty well actually.
As far as putting put a banner for something like host monster or other large host, not a chance. But then I won't post a link on our busienss site that is a service that we do not or have not used personally. Our name and reputation goes on it, so we're very careful about recommendations in that regard.