I've been folding stash most of the day, trying to rearrange. My prior sorting was along size. Fat quarters together, half yards together, etc. Not very organized to say the least. Earlier today I started resorting into color. But I found this rather hard, as I am quite the Magpie for bright colors and bold prints.
From reading this thread I think by designer/company might work best for the majority. Most would be considered modern and a good chunk is Alison Glass, Frances Newcombe, Momo, Carolyn Friedlander, Lotta Jansdotter, Cotton + Steel, Michael Miller house designer, etc. That and solids/blenders by color would probably take care of 75-80%.
Or just make a big jumble called "Misc" and consider it all sorted. : )