This got some discussion as the "Hipster PDA" some years back (originally 2004 from Merlin Mann), along with some low-cost options to simplify managing it - mul

This got some discussion as the "Hipster PDA" some years back (originally 2004 from Merlin Mann), along with some low-cost options to simplify managing it - multicolor cards, bullet journal rules, cutting out card-sized pieces of plastic from a cheap folder to make a "cover" and of course various sizes of binder clips. I found a medium to large binder clip to work better than hole punching and a ring - you can't just open it up and use it while standing, but it holds together better and easier to add/remove cards. A big advantage of this over journals (Moleskine, Field Notes, etc) is that there's no mental block of "I don't want to write something stupid or trivial in my journal/notebook."