A couple problems which many 3D printing enthusiasts experience are the clogging of the extruder caused by dirt or debris on the filament, as well as wear and tear on the extruder motor from over use. One design for a 3D printable DIY filament filter can take care of both these problems.

Creative tools has uploaded the design for what they call the Universal Filament Filter. The device is easily printable, and will clean your filament as well as lubricate it prior to it entering the extruder. More details on this device and how to print and make it can be found here: http://3dprint.com/18293/filament-extruder-filter/

Check out a picture of it in action below: