Depreciated: This item has been replaced by version 2, a 100% printable spool holder, located at http://www.thingiverse.com/thing:8317 Please refer to that file, which is a much better design.
I liked BrokenToaster's idea of a bearing-driven filament spool holder, but that version was too big to fit on a Makerbot print bed. I separated the arms from the hub, making a tight-fitting dovetail joint to connect the pieces without any hardware. It now fits on a Makerbot print bed!!!
EDIT: At Wajazn's suggestion, I added a version that integrates a printable bearing from http://www.thingiverse.com/thing:4312 . Disclaimer, I have NOT tried to print it, but it should work.
UPDATE: (1/22/2011) I added a solid version of the integrated bearing hub that has no spokes to avoid the problem people were having with one of the hollows printing solid. I just skeined it in 0035 and it looks good.
You only need one of the two "Hub" files. Spool Hub uses a 608 bearing, Integrated Bearing Hub has a printable bearing. I_B_Hub_Solid is the most recent version that prints a little better (at the expense of a little more plastic). Pick your poison.
Print two hubs and 6 legs. Clean up the parts if necessary but try to resist the urge of sanding the holes or the dovetails. Unless your settings are way off, they should fit together (very tightly). The ridges left from each slice of the print actually helps hold the piece together, so leave them if you can. You should be able to push the pieces together, hearing clicks as the ridges snap past each other. You may need a soft mallet to hammer it flush. The joint is strong enough where no fasteners or glue is needed. Print any other parts for the stand that you need and assemble according to the original parts' instructions.