A couple of updates. I like Mia Ridge's post on QR codes. 'Tinyurls you can wear' is a good description, in most of the people who I'd have to explain QR to wouldn't know what a tinyurl is either. Dan Pett at the BM also points to Google charts for creating the codes. This shows the maximum character limit varies, so the best solution would be to choose the smallest resolution possible and show it at the largest size to get round the limitations of projectors. Using Tinyurl or Is.Gd would be a way of doing that.