Whoever does need it, I give you permission to throw out all your old cables, power adapters, and routers. Yes, on the off chance you do decide you need a Palm III dock, Linksys WRT54G, or Sony PSP charger that means you'd have to buy one on Ebay, but you can cross that $10 bridge if it actually happens.

No, this method does not work. I tried, got rid of all those stuff because why would I need it ever again. And of course a month later I needed that one stupid thing right there and then. And I remember throwing away... Not again, I keep at least one cable of each in a separate box to find immediately, the rest is stored, it is not asking for any money.

For me it's not the cost that bugs me when I don't have a part, but rather the disruption to my flow. If I can't get a project done all at once I'm much less likely to ever get it done.

I have a bin of cables marked "Obsolete". A cable only goes in there if there's absolutely no possibility of it being used for any reason ever again.

I use cables from it once every few years.

And whoever needs something else, I give you permission to ignore this fool and keep your box(es) of cables. I don't regret a single thing about my ~8 boxes of cables.

For me, the hardest part is actually figuring out what the cable is called in order to find a replacement.

Throwing away proprietary cables is a sin. Throwing away standard commodity USB cables is not so much