I think most of us organize our stash the same - by color. I wish my favorite fabric store would do that - its so much easier to find what I am looking for. But they claim that most of their customers are looking for lines: Moda, RJR, etc, so they keep them that way.
My stash, and I know I am very lucky to have a large closet with coated wire racks for shelving, is organized mostly by color. But I have large rubbermaid storage boxes with future projects set aside, Christmas prints, Halloween fabrics, kiddie prints, patriotic fabrics, and the bin for my only client's projects. Since my kids are grown I took all the solid oranges and yellows out of the Halloween fabrics and put them back into the stash piles.
I have one shoe box for scraps, and one for all the log cabin strips leftover from my Leaving California quilt. (These are new to my sorting habits. I spent most of a Saturday in April reorganizing the sewing closet.) I throw leftover strips in there so I can make a Log Cabin from those someday. I don't hardly ever buy quarters, but when I do it's for an immediate need. Anything left over is in the stash pile of that color.
Anyone who visits and sees this closet asks when I am opening my own fabric store. LOL :wink: