I use OS 1:50K and 1:25K. I remove the covers on purchase, mark all 4 corners (of both sides if printed that way) with the map number in thick black felt tip and then refold the maps half/half/half etc.; the new folds coupled with the original folds mean I can generally refold the map any old way for my mapcase using both sides for a hike, where necessary. They are then stored on their edge map number up in a cardboard box suitably sized, at least 1:50K ones are as they're a uniform size. The 1:25Ks are stored on their edge, between bookends on a bookshelf. In order. I also have an XLS spreadsheet listing each map so I know whether I have a particular one or not.
My other maps, Nat. Geo., ITM, etc. are in organised piles on a bookshelf, folded in their original forms.
I find maps aesthetically pleasing too.