I also tend to save usable materials for projects and repairs: lumber/plywood, masonry, glass/plastic, metal, computer parts, etc...
I'm glad someone else does this. I'm getting like my father and have jars of screws and nails, some used starting to clutter up the place.
Old credit cards are handy for that quick glue or wall filler job. I have loads of cards in waiting.
I use used (washed) old microwave meal cartons to re-use in the microwave - have lots of them.
And, I'm a little ashamed to say - I have a huge collection of Pot-Noddle pots for storing thing in. I did chuck quite a few away recently in a purge.