I saw Bonnie Hunter's system and cut some things up into various sizes and shapes. What I now see is that I prefer to use only 3 sizes when cutting up scraps.
I cut them into 2.5", 2" and 1.5" strips. That's all. It's super easy. If they are larger (like fat quarter size) I put them back with my fabrics unless I know that I will NEVER ever make a quilt using that fabric (for me, that means Mardi Gras, Elvis, etc.). If that is the case, I will go ahead and strip the whole yard or so I may have acquired (usually in an assorted "lot" of fabrics).