I recently went to a Scrap Club class where the instructor showed us how she takes her scraps and turns them into quilts. She recommends 2.5" squares, 3.5" squares, 5 inch squares, 3.5" X 6.5" bricks and finally 2.5" WOF strips- just think of it as making your own pre-cuts. I purchased plastic shoe boxes and as I finish a project, I decide if the leftovers will go into the scrap container or cut up to go into one of the above boxes. I found that using an index card put inside the end of the box (so I can see on the shelf) is easiest since I now cut more sizes than the above. I also keep Christmas and Holiday separated from the others. FYI - got the shoe boxes at Costco, Iris-the lids don't crack like other brands and they fit snugly together. Once you get enough cut, you can make a scrappy quilt with any one or a combo of the pieces without buying more fabric for the top.
ANOTHER "REASON" to get more fabric so you can fill those scrap boxes. It is also a great way to have that last minute "quilt stuff" for a gift project. I have "stripped" leftover holiday strips-Halloween quilt leftovers- onto muslin and will turn it into a table topper.