Here's one I haven't seen. Is there a rule of thumb perhaps for what percentage of the visitors to any commercial website actually respond by e-mail or phone? I get one out of every 15 to 20 visitors to ask for more info. Of course I think it should be much higher and that there's something inherently wrong with the design of my websites, but I thought I'd ask.
Last place I worked we averaged 10% to 15% response rate from folks that visited the site and that was from highly targeted email newsletter and banner advertising traffic. I don't know if that's a decent number or not but I may help give you a frame of reference.