It's not that easy to find a solution to make sure the filament doesn't get stuck during a print. After hours of browsing thingiverse, failing with a couple of spool holder designs and a ton of canceled prints because of filaments knots I started from scratch and came up with a new approach: the filament duck ("inspired" by a duckbill). I used the low quality profile (3h). I recommend to use helper disks (in MakerWare: File -> Examples -> Helper Disks) or even a raft to ensure that the first layers don't raise from the bulding plate during printing. If that happens the product will be usable as well but the stand won't be even. The model has little holes for use with small rubber feet for secure standing.