the memories come flooding back...
I saw this blogged a couple of days ago but the seeing the DIY version jogged a memory... my dad used to use a tripod like this 20 odd years ago on family holidays.

His was the lid of a large jar of coffee (about 10cm diameter I guess) with a similar screw arrangement to that one - wingnut under the cap to tighten it. A shim under the nut was used to make the 35mm camera sit at an angle if needed - the shim was pretty much anything to hand, and being kids on holiday, lollipop sticks were in most hands.

Having the wide base meant the camera sat quite stably without the weight of a watter bottle, but as it was short you needed something to rest it on - a wall, a table, or the car.

Them war tha days.

flimsy
won't hold my cameras (3 large SLRs with powerpacks and heavy lenses) but nice for small P&S cameras.
Simple pocket tripods are as cheap and sturdier, plus you can drink what's in the bottle instead of having to preserve it as counterweight for the camera >:-)

Adjusting the angle
Another problem with this bottlecap tripod is that you can't adjust the angle of the camera. What if you want to point it up or down? Can you think of a modification for this design that would allow you to do this?

Real tripod for $3.13
I'd rather have one of these in my backpack than a bottlecap "tripod": http://www.wdclub.com/catalog.cfm?do=details&itemID=849

Adjusting the composition
You'll usually want to compose your photo. Simply push the bottle into an empty boot or shoe. This should hold it upright and allow some range of motion to adjust your composition. This technique will probably not work with 1-liter bottles unless you have NBA-player-size feet. With a little thought I's sure anyone can come up with other handy objects to stablize this kind of tripod setup.

Exilim tripod mounts?
Does anyone have any tips on making a tripod mount for an Exilim EX-S2 or similiar? They lack a 1/4-20 mounting hole, so I've tried a couple of zip-tie and rubber band contraptions, but none has been satisfactory...

Use a bead filled pillow
Use a bead filled pillow to change the angle of the bottle. Simply mush around the form until the bottle is supported at the desired angle. It's like having a bean bag chair for your "tripod". They are available at Brookstone under the name "Fom" with one of those lines above the o to make it pronounced as a long syllable. They also make for comfy travel pillows.