Wind Turbine
Here's some sample links on building your own wind turbine. They're currently unsorted; what's needed is analysis, in particular, whether there are any designs that can be used by RepRap.
Collection of links from otherpower.com
How to Build a Chispito Wind Generator
Note: does have motor and other electrical parts listed - may still need to buy these
DIY Instructions for making wind systems at home from yourgreendream.com
Again, needs a generator - they suggest from a broken Fisher