When I was at school there was a lot of old Mac software sitting in boxes in cupboards and drawers. Quite often it would gather dust and then get chucked out - fortunately I managed to save the vast majority of software before that happened to it. The school was always glad to give away their old stuff to someone who would appreciate it.

Computers tend to rot quite quickly if they are left outdoors in the rain for any length of time. I have rescued a couple that have been out for a couple of days and often after drying they work fine. Once I even found a SE/30 that looked like it had been out for at least 2 weeks and after stripping down, cleaning and drying it worked perfectly (and still does). Once rust and other corrosion kicks in though there is generally little hope.