More of a test and showcase of an idea than any fancy new design; it doesn't get much simpler than this.
Please go ahead and make larger sizes too. :)

Until sensible packaging that's biodegradable or easy to recycle becomes more widespread, in a pinch you can fill out any gaps around packages you have for postage with these little cylinders.
On output, they seem to be reasonably stiff, easily springing 1mm or so in diameter with a strong squeeze, and breakable at a few millimetres. They could be used to replace expanded polystyrene 'packing peanuts', whereever scrunched-up paper is too squishy.
It might be a good idea to cut a small amount of the material out of the model to reduce stiffness even more.

The cylinder included is 15mm long, with an ideal Inner Diameter of 9.5mm and OD 10mm, the resulting effect being that a 0.5mm extruder nozzle will draw a circle one-line-wide on each layer, which should shrink to be a loose fit around M8 bar/studding.

This gives the part three simple purposes:

1. Biodegradable packaging
2. Circular print test/calibration
3. Spacers and/or protective sleeves for M8 fastenings

Generate a plate of them using Skeinforge's multiply tab and print away!

(I tried exporting an STL with a pattern of parts to slice up, but skeinforge took about as long over slicing the first layer as it did to create the entire equivalent gcode for a single cylinder multiplied within the program; must be something to do with how SF approaches the problem)

A sheet of 64 (8 by 8 closely spaced) took about 1h15m to print with 20mm/s perimeter lines and 60mm/s moves.
I also found that my old Adrian's Geared Extruder began to lose grip on the filament by the end of the print, giving me a good reason to try and add a cooling fan to it or build a new version of Wade's extruder.