I save them. Started organizing by size once upon a time. Didn't stick with it.
I saw an old Kaye Wood show where she just stitched them to each other and kept rolling them up. When the roll was large enough, she could decide how long or wide she wanted the quilt/pillow or whatever and just cut strips from the roll for a very scrappy quilt. I think the scraps were all the same width but different lengths and colors from all her projects. Sorry I don't remember the exact details.