I store most of my internal PC components inside a Dole Banana box (see non-exhaustive illustration below on how I got it situated). However, there are exceptions to this rule, specifically CPUs and spare CR2032 batteries.

I store my CPUs in a small box inside my testing desk's drawer, there's a foam pad between the bottom of the box and the CPUs to prevent the pins from getting bent. My spare CMOS batteries (mostly CR2032s) are stored in a Ziploc bag in that same drawer where I have my CPU box stored.

I have another Dole box which contains misc. parts which include random laptop parts and proprietary oddities from other systems.

As for motherboards: I only have one spare motherboard which is stored in the bottom drawer of a square 2-drawer cabinet.

I try to put most things back into their original boxes for storage since the original boxes protected them in the first place. For things without their original boxes, I try to use whatever box they came in along with the packing material. Takes up a lot of space, but pretty much guarantees nothing will get broken.

martin939 wrote:

Mainboards en GPU's go in here: https://s.s-bol.com/imgbase0/imagebase3/large/FC/7/9/6/5/9200000002755697.jpg Placed vertically […]
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Mainboards en GPU's go in here:

Placed vertically, next to each other. Each one labelled and put in an anti ESD bag. The 2+ slot GPU's I have on display on the shelf.

Same over here. A large furniture store from Sweden that ends with 'kea' sells those containers really cheap (but it does add up if you have a lot of crap like I do haha).

I also store old magazines and software boxes in them, so they don't get eaten by silver fish who love them 😒

For CPU's I have small carton boxes, just large enough for anything up to the dimensions of a Pentium Pro. You can place anti static bubble foil or foam pads inside to protect the pins.

If you have a lot of CPUs, search eBay for CPU trays. I don't know if there are any available at the moment, but they have come up before. I bought a stack of those trays and keep almost all my CPUs in them. Very safe and compact.
I have 2 types of trays, most of them are the type that holds older PGA styles including socket-7, socket-370, and Athlons. The other is a different style designed for mPGA478, but I've also stuck LGA775 in them (they slide around though).
I think my early Socket-4 Pentiums fit the PGA trays but I don't remember for certain. I don't remember if the K8 chips fit either - they might fit the mPGA478 trays but I have mine in those OEM plastic clamshells.
The Pentium Pro definitely don't fit. I have mine in a small box, I think with antistatic foam.
Slot CPUs are stored a bit haphazardly, but they're almost as indestructible as heatsinks.

I have too many motherboards. I try to store them vertically in a box, most of them in static shielding bags. Their size makes them more vulnerable to strain from bending.
General expansion cards - kind of a mess.
Video cards are less of a mess, but too many for the box I have them in. Most are in static shielding bags. A few are in their own boxes if I consider them more valuable.
My most valued sound cards are in a luxuriously sized box with a lot of padding, because these things are like gold and somewhat failure prone IMO. I worry about them.
My most valued hard drives are in a 5-drive foam shipping container. The rest are piled up together in a drawer that's lined with bubble wrap.

Note that static shielding bags are not the same as antistatic bags. Antistatic bags are those pink bags which don't generate static, but they don't shield against it either. The metallic bags will shield against static passing through. Use those on the things you value the most, and pay attention to the physical condition of the bag - beaten up ones don't work as well.
I think a lot of people don't realize the pink bags don't shield. It's funny how many sellers I've come across who use the cheaper pink bags, surround them with static-generating generic bubble wrap, and attach warning labels about ESD safety.

I have just bought a set of 50pcs of those plastic CPU boxes but they'll only hold LGA478/775/11xx series CPU's. S.370 or 423 is quite problematic in this regard.
They also sell AMD clamshell boxes but they have that weird long shape because AMD also puts the case sticker into it.

@
SpectriaForce,
Not really worth a trip to Aai-Key-a, I get mine at Action, dirt cheap.

I use wooden shelves/scaffolding (like those IKEA ones) and they do the job of storing boxes of parts quite nicely. I also store some computers there; http://i.imgs.fyi/img/24mi.jpg