Still have my doubled C64 floppies, of which some were horribly scarred by the big blunt scissors I started out with.

You could also convert Amiga floppies from single to double density by adding a hole, giving you 1760kB. I didn't have money for quality disks, and found that "punching" the hole with a hot soldering iron lead to less problems than using what was probably the wrong bit in my dad's drill.