This is the first time that we've done this but I think it worked pretty well.
We'll improve it in coming open houses, but building in an auto responder with the area info, listing details and comparable area listings, sent to their email address, proved to be a good idea.
It's ecologically more responsible and at the same time it encourages our mailing list to grow, so it's good on multiple fronts.
Here is the video I shot that outlines the benefits (and weaknesses) of the system.
Additionally, we had a live stream happening using ustream.tv - I recorded it and got the following video footage. The only drawback was that we did not have functioning audio on the laptop I was using, so therefore it has no sound unfortunately... oh well, next time.

