Filament clip

I've been storing my filament on cardboard spools http://www.thingiverse.com/thing:1550 which works fairly well, but the plastic likes to unroll itself. Clothes pins are mostly effective to hold it on, but they are easy to bump and knock off.

Here is a fully parametric model for a simple clip that will slip into the edge of the spool, with a hole in it just the right size to hold onto your filament.

This clip is good enough for filament that is just sitting around, but if you wanted to ship it, probably you'd want something you could screw down or maybe add tape to this as well.