Found laptops on the street fully abused and often smashed to bits. Recently pulled a 160gb SSD out of one. That’s worth keeping, as well as the RAM, often.

TV tuners/media players: they sometimes have internal hard drives. I recently pulled a 320gb 2½″ HDD out of one. Even though that’s likely too small to serve as someone’s laptop system, anything bigger than 120gb is big enough to store a copy of the whole Debian system including all apps (5 blu-rays merged these days).

All DC powered electronics: it’s useful to cannabalize the female barrel connector. There are many universal PSUs with a collection of male tips, but never female tips. The female tips are useful for making your own barrel adapters, instead of cutting and soldering your OEM PSUs.