Most recently I end up donating some to our local pub, because everytime I try and go in there and do some impromptu magic, I end up using their beer stained sticky pasteboards.
torn and restored, mercury folds, building houses of cards using selotape and baffling our friends, rolling them up to practice cigarette tricks, practicing splitting cards, there are many many thigns you could do
perhaps you could gather all the doubles of 1 particular card, hide them all around the garden @ a bbq and after forcing it on them, point out all the doubles in the area.