When at a convention, there's a lot of standing, walking, and carrying of heavy things followed by achy muscles. One bit of gear I wish I had remembered to bring to the last convention was this
I find it to be a great portable back massage tool (some people like a racquetball instead). I just put it between my back and a wall, lean in, and move around a little to relax some of the muscle knots. This plus a bit of gentle stretching seems to do the trick.