http://blog.beechmountainbliss.com/2009/12/making-do-tradition-of-mountain.html
And after receiving tons more non-working tree lights from the very nice folks who live in my area (I posted a request for them on craigslist, and several people gave me their old lights instead of tossing them. I love craigslist.), I have been working a lot on coming up with new design ideas for ornaments. (And I suspect that there will be a lot more postings to this blog of ways to use 'em in non-Christmas ways too.)
Anyway, if you happen to have some clear plastic beads on hand, an arrangement of these, glued together can replace the balled up piece of tin foil as the core of your ornament. I glued 7 clear beads into a symmetrical shape (As you can see in the photo, I started with 3 in a row, then added 4 more around the middle bead.).