There are a lot of spool holders out there available for purchase or 3D printing. However, one company, called CreativeTools, has created what might just be the "ultimate" 3D printer filament holder. It can be 3D printed at home, and is able to hold virtually any size filament spool, as well as unspooled filament. It features rollers so the filament spins as it is used up, and even includes a filament filter, to ensure that your filament stays dust-free and moist. What do you think? Read and see more at: http://3dprint.com/20280/3d-printer-spool-holder/

Below is an image of CreativeTools' Universal Stand-alone Filament Spool Holder: