Quoted from halflip87:
I work a lot of trade shows for my job and many of them feature some sort of "scavenger hunt" to encourage attendees to visit vendor booths and allow the vendors to generate more potential leads.
Basically, all attendees receive a card listing the names of various vendors which they have to visit and get a signature/stamp from. Once their card is complete, they submit it to be entered into a raffle for a nice prize. I think this would increase traffic through the vendor hall and give incentives to both the attendees and vendors.
Interesting idea. I'm not sure if vendors would like to be interrupted all day by people looking for stamps at their booth, though.