Image Credit: Joe Shlabotnik
I am sure a lot of green folks like me hoard or save things because you:
a) Don't like waste
b) Never know when you'll need said items again
c) Have some psychological disorder
d) Like me...all of the above
So here's a partial list of things I save. I definitely got this trait from my grandparents, who as adults in the depression, never threw away anything. And I mean anything.
The moment you toss it...you'll need it.
Nuts, bolts, screws, nails, etc - It doesn't matter where they come from, I never throw away this stuff. Even the oddest screws end up finding use at some point.
Scrap metal - I keep almost all of it. I remember on the farm, my grandfather kept all the old tin cans...I even made a wall mount for the LCD iMac in our kitchen out of a scrap piece of tin. Saved me over $100 by not having to buy a specially made wall mount.