One thing my son and I were interested in was powering a Raspberry Pi from batteries. At present we have no specific application for this, but obviously if it can be done it opens up a world of opportunities for a portable Pi!
To this end I popped into my local Maplin store on my way home and picked up a 4xAA Battery Box (Code HF29 - £1.29) and a PP3 Clip (Code HF28 - £1.19) to go with a micro USB cable I picked up at Poundland earlier in the week.
I snipped the USB plug (the big one, not the micro one!) from the end of the cable and stripped back some insulation. I then snipped the yellow and white wires off and connected the red and black wires to the same colours on the PP3 cable. This then clipped onto the battery box which by now was filled with batteries, ready to rock.
We connected up the Pi and it came to life! Booted OpenELEC and started a video playing, all without problems. Very pleased.
We might make a further trip back to Maplin this weekend to pick up a switch and some rechargeable batteries, I'll keep you posted!
EDIT: Tweeted about the above, and the Raspberry Pi people dropped me a tweet back to say "awesome - but be aware that if you push more than 5v through you may shorten the lifetime if the chip. 5v linear regulator FTW!" Hmmm... obviously this isn't quite as simple as I thought and a bit more work is required! In short, don't follow my instructions above for now, will update when I come up with a better solution.