It depends on the value and rarity of items. If I have some ISA card that I know goes for 50-100€ I can easily stash it away until I feel like selling it. On the other hand, I try not to get any 00's hardware as it is still pretty much worthless and there's no real profit to be made. Problem I have is that I know some of the stuff would be close to impossible to sell locally, so eBay is pretty much the only option, but then I'd have to install and test all the things to make sure I get the best price and that's just too much trouble. So basically I know what I should sell and where, but I'm too busy/lazy to actually do anything about it. 😵

eBay first, if necessary. Second, I mention them in "advertisement" section of local news papers. Third, friends.
If nothing works, I remove the valuable parts and take the rest of it to a recycling center.

But in reality, I just keep them most of the time and box them up nice and tidy (at least I try to do that). 😊
You never know when you need recycling parts. Even ISA slots of a defective board *could* be handy sometime in the future.
Imagine. maybe in the not so far future you get that crazy idea of building that ISA slot expander box and need them.