Windmills , there is a lot of information here about historic and modern windmills and their uses. I got sidetracked by this site for more than an hour when I stumbled across it. Did you know that windmills were a primary energy source for flour milling during the colonial era of the US? Every farm neighborhood had one or more.
Windmills and how they work , nice little page explaining windmills, has diagrams and pictures.
Windmill design and construction , "windmills were works of art, no two were ever alike," history, design, milling.
Mills of the 18th & 19th centuries in Camden County, North Carolina , nice site describing early windmills in this area of the US.