Thanks all! Some great suggestions. I generally keep the little bags they came in, but if I buy a bag of 3, I'm not so keen on putting a used leader back in the original bags (since it will no longer be 9' or 7-1/2'). And there have been times when I've taken off a really tangled leader, knowing that when I get home with good light and warm(er) fingers I can untangle it.
Of course the major problem is remembering which leader I have on the rod from the last time I headed out. I think I'll end up developing some kind of color coding (using a sharpie) on the butt-end of the leader, and put some kind of label on the bag (or bag insert) so I don't forget. Age is having its effects!