We are sorting out the details related to this very topic as we speak. Sean and I are putting together a directory, actually two. I have been discussing the plan with Dana as well, and we are all on the same page. Currently, there is no single place where they are all listed in a webpage.
One of the problems has been due to the technology - in order to put banners into the forum software we have had to hardcode in different locations and it would be a lot of work to put a new webpage together with all of the banners or links.
We are considering putting all of the sponsor information into a database so we can generate an alphabetical listing of sponsors in HTML that will always be current and correct. That way when sponsors join in or drop out we don't have the horrible code management problems we have today.
Short answer - not yet!