The Deltaprintr is about to launch on Kickstarter. It's a personal 3D printer with a difference: the device uses a delta mechanism instead of the traditional cartesian XYZ axes.
It's easier to understand if you watch the video. The extruder is oriented by changes (or deltas) in the three vertical posts instead of sliding back and forth on three X, Y and Z axes.
The advantage of this approach is accuracy, simplicity and lower cost. The Deltaprintr offers all of these: 0.1mm accuracy, no required calibrations and sub-USD$500 cost.
There's one more interesting feature: the vertical axis can be extended beyond its original length. In its standard configuration, the Deltaprintr has a 254mm diameter by 305mm height cylindrical build volume (this is specified as a cylinder due to the delta approach; standard 3D printers have a cubic build volume).
To reduce cost beyond the fewer parts required in the delta design, the makers have used "highly tensile" fishing line instead of belts to drive the extruder.
The PLA plastic-only device is not yet available, but we understand that it will very soon be launched on Kickstarter, where you'll be able to procure one of these interesting units yourself.