I have been mulling this one over, myself. I hate using the eye's and having a whole feather (practically) left over.
So far, my best ideas are to;
Turn them into a small, shimmery nest.
I just trimmed a thin-ish section about 6" long. Then 'broke' the spine, gently as to get it to bend into a circle. I decided to wrap it with some sparkly floss thread, just to add dimension and cover the white spine part (a tiny bit of hot glue helped the ends stay down) and make sure you let the shiny feathers hang as far out as you can manage as you wrap. Basically now you just make a small wreath out of it... bend it into a comfortable circle (should be easy since you gently broke it before) and keep looping one end through the center, until its round and you have used it up. Then wind/weave all the feathers in (I added some extra feathery bits for fullness). I recommend a smallish gauge crochet hook for the last part.
You can trim the feathers off the spine altogether. Just that shiny strand is fun to accent things with. Glue them into bunches and hang them out of fittings (or wrap them with floss and seal with nail polish or glue) for earrings, pins, pens or really about anything for some subtle feathery flashes. They also hold their shape well when applying glue or similar coatings.
I actually painted my nails a while back, then when it was still a bit wet, pressed a bit of feather strand into it and sealed it on with a clear top coat. I was impressed at how neat it looked!
I had no idea other people had the same problem as I did with these things
Hopefully you can come up with some fun things to do from here!