I just returned from a large, well managed conference in Portland (you know the one), and this was one of the ideas that stood out as excellent, at least in my opinion: Sticker Table!
People leave stickers, take stickers, and see stickers. It's a great way to give your project more visibility and it's also a great way to see what other projects are around, and possibly even at the show/conference.
Have you seen anything at recent shows that made you say, "Wow! Great idea." Please share in the comments or shoot an email to randall at ubuntu dot com.