I keep extra microsweitches, since I can't find them locally... I bought some non-Cherry "sale" switches at Happ's (
http://www.happcontrols.com/wp/item_search.html?item-no=95-1436-00 ... 10 switches for $3.80); they take a lot of force to actuate, though. Might be good for an Ultimate joystick, probably not as good for buttons...
I keep lots of everything. Whenever my work disposes of something, I strip it of anything remotely useful. We had a lot of old P75 cases get tossed, and before they went I took the LED's, the fans, the power and reset buttons, the fans, etc. When my cordless phone burned out, I kept the AC adapter; if nothing else, it's wire! Because of that, when I built my cabinet, I had so much scrap around that I had to buy very little. Wiring harnesses were built of bits of scavenged wire and connectors; those LED sockets I've scavenged over the years found their way into the control panel; the fans are installed in the cabinet vents; even metal drive bay covers have found new life as mounting brackets.
--Chris