I dabbled in a bit of neography (creating your own writing system) and a hint of conlanging (creating your own language). I think I've managed to create a fairly decent writing system for myself, but the conlang went nowhere fast as I underestimated the effort required to even get started with it. I also attempted making fantasy maps, but it was all in paper and quite a while ago.
That's it, I suppose: neography, conlanging, and fantasy mapping.
I also spent an embarrassing amount of time looking at maps and making virtual road trips via Google street view, but that's way more mainstream.