Summary

A modified version of the original Eventorbot spool holder. This one has less overhangs and provides a mini bridge to hold the end up while printing.
It's a little big--I have a couple spools that won't fit on it.

NOTE: I have found that this spool holder is convenient for certain spools, but has too big a diameter and is too short for many spools.
If you are looking for a more versatile solution, I would recommend this:
http://www.thingiverse.com/thing:186368