I have a rolling computer case instead of a backpack, but much the same kind of stuff inside: computer, power supply, mouse, cellphone, USB chargers, cables (USB with interchangeable client ends and Ethernet), paper, pens, business cards, coffee cards, travel club cards...
Not nearly as much fun stuff as yours, though, Max.
Over at Microcontroller Central, one of our bloggers (Adam Carlson) has written about the portable development toolkit he keeps in a backpack. Seems his day job is not about electronics, so in order to work on his home electronics projects at lunchtime, he created this carry-along lab bench. Check it out at Create a Portable MCU Tool Kit
They were giving iPad cases away at Design West? I missed that ... but it really doesn;t matter, because I can't see me ever not using my leather iPad case from Saddleback Leather ... this just "Stands Proud in the Crowd" :-)