I hoard all those useless bits of wrapping paper, old cds, bits of ribbon - almost anything in fact. It all comes in usefulf for Brownies. If not for something specific, I take a huge bag full of rubbish in & get them to make something - I might give a theme such as the loch ness monster, or leave it up to them. Then they get to take it home at the end of the evening. So their parents will have more junk!
If anyone can come up with some craft that uses those plastic balls you get on the top of Persil I'd be grateful - I have hundreds of them!!!