The Paint Machine Blog has an excellent, multipart tutorial on painting ancient spanish scutarri. A nice touch is that he tells you how long it takes to paint each step.
Painting Guides
Painting Camouflage Pants
Studio McVey has a short tutorial on painting camouflage patterns on a pair of pants.
Viking Painting Guide
Crusader Miniatures has a painting guide for Vikings.
World War II Painting Guides
Artizan Designs has a page with very good painting guides for a wide variety of World War II Uniforms.
Armies of Finland 1783 – 1811
The New York Public Library has a large collection of color plates of the armies of Finland in the 18th and early 19th centuries.