If you love breaking things apart to learn how things work, or if you simply have a bent on tinkering hardware and/or software, then you are more likely be having a career in IT.
You may have heard of the following already. If not, just read on and tinker with it.
Linux – nuts and bolts of OS
Arduino – hardware
openQRM, OpenNebula – networking
Proxmox, Xen, KVM – virtualization
MySQL – DBMS
And many others…
That’s the beauty of open source: it encourages anyone to read and tinker with the code. With GPL, you are required to share your contributions. In contrast, with BSD and the like, you can keep it to yourself.
Regardless, open source fosters tinkering. You can’t do that with proprietary software. Well, that is as far as tinkering with the code itself is concerned.