I regularly visit fairs or attend development sprints, and in the course of a few years I've gathered together something I call a "mini booth-box". It's a plastic crate full of odds and ends that are invariably useful at an event; I can either take the whole box or cherry-pick from it for specific events. Like at FOSDEM this year, where I packed 2 19" flatscreens, a Sun Ray, two keyboards and mice and a laptop into my backpack. Forgetting, of course, the required switch and stuff. Well, the best-laid plans ...
Anyway, here's a list of what's in that crate, in the hope that it might be helpful for someone else.
Networking: A 24-port hub and its power lead; a 5-port switch and its wall wart; a WRT54GL and its wall wart; a crossover cable; 25m, 10m, 2x5m and a 2m straight UTP cables. Video: DVD-D dual link cable; VGA D-sub cable. DVI-I to D-sub adapter. Input: PS/2 mini-size keyboard; USB keyboard; USB mouse. Misc: 1GB USB stick; bluetooth dongle; 1m eSATA cable; 1.5m USB A-B cable; 1.5m USB A-mini cable; Nokia phone carger (mini-connector). 4-socket power strip. UK-Euro plug adapter.
I know some of that is redundant, overly specialized or just crap, but it serves its purpose of giving me a one-stop shop in house for picking up equipment when going to a fair. I just hope I didn't forget anything. The Sun Ray thin client doesn't travel in the box, but it does good service at stands if I want to use my laptop while at the same time leaving the laptop at the booth for display / demonstration purposes.