Here are some feather studies I did while at work. The two feathers on the very top of the page (the ones that have a brown tinge to them) are the actual/real feathers. The other three are drawings. The real feathers were, of course, used as models, except for the bottom-most and smallest feather, which was simply sketched for fun and for additional texture study.
Each of these took anywhere from a few minutes to maybe twenty minutes to compose. I was going for detail more than "anatomical" accuracy.
Photoshop CS3 was used to darken in the image just a tad.