This is a three blade wind turbine. Just connect to a small motor and you can get up to around 1.4 volts in a good wind current. It can double as a miniature fan, if you connect the motor up to a battery instead. This is my first finished design for Thingiverse!
There are two parts to be printed, blades and a holder hub. The blades print vertically, as does the hub. You have to print 3 blades for this project. After printing, the blades snuggly fit into the holder hub (and could be glued for a stronger finish). The .stl files should be ready to print for a Makerbot. I found that on mine, rotating the orientation of the blades can affect how they turn out, because of where skeinforge starts and stops extruding for each layer, so I have them turned as best printed from mine using skeinforge 7.
I designed it all using OpenSCAD. The nice thing with the blades is that I have created a bunch of variables that users can modify - so you can take my .scad file, and easily tweak the blades to be: longer or shorter, more/less curved, thicker and thinner, and wider/sleeker. Then just recompile and print! This uses a .dxf file created from Inkscape to provide the general blade shape and uses the linear_extrude function to convert the 2d representation of the blade into a 3d shape. Quite fun.
To make .dxf files from .svg files, use pstoedit. I've included my makefile to show how this works. (1)