I was going to post this earlier in the week but with Valentine's Day, I thought I'd better wait!
1. Check out the barbs and barbules - the tiny feathers that come from the shaft or stem of the feather are called barbs. Off the barbs are barbules which have hooks like velcro. If you smooth a feather the wrong way (top down) they get all scraggly. Then clean them up by can pretending to preen and smooth your feathers the right way. The barbules will re-hook and the feather will be smooth again.
2. Dip them in water. What might happen? Older feathers, or those that are dyed, might just get wet, but on fresher feathers the water will bead up. Birds have oil glands that they use to keep their feathers water resistant.
3. Paint - paint with the feathers using slightly runny paint or water color paint. Different feathers will make different patterns.
4. Make a game. Tie up a bundle of feathers to make a shuttle cock game played by native American children.
Here is a description.
5. See how long you can keep a feather in the air with your breath. Blow the feather up in the air and you can count or use a stop watch to see who can keep a feather in the air the longest.
I collected these feathers just from my backyard. I can remember as a kid hearing that I shouldn't pick up feathers in case they had germs. Well "germs" that affect birds don't usually affect humans. Yes, there is an avian flu but it isn't going to be carried by your average backyard bird or their dropped feathers.
One thing to note is that you cannot pick up feathers from migratory or endangered birds. Just don't even think about it. What you see above are Turkey, Blue Jay and Mourning Dove feathers.