The $1 Image Stabilizer (aka The Stringpod)

Clever!!!

I used to have one of those, I tied some twine to a retaining screw liberated from my SLR's unused ever-ready case (remember those?), and put a loop at the end to put my foot in. I think the washer approach might be better though, since a loop tends to hang closed so it's hard to slip your foot into it unless you fiddle about with it. The main trouble is the string soon gets muddy so you don't really want to put it back into your camera bag!

Another trick is to carry a lightweight tripod with a string net or bag slung between the three legs, and when you set it up, fill it with rocks or books (whatever is lying around) to give you the stability of a heavy duty tripod. You can also use the string approach here: hang a string from the centre column and stand on it to tension the tripod.