when making humanitarian quilts, i work with squares down to 3" and use the smaller ones more for the baby sizes.
its nice to go thru my pieces, and cut as large a square as i can ...then put them into seperate boxes. i prefer the 1/2" sizes ( 4 1/2, 5 1/2, etc)...makes it easier to count how many blocks you need. (a 9 1/2" makes a 9" finished block, therefore, it takes 9X10 for a 90" wide quilt....then figure how many for the length you want.) 9 1`/2" comes out perfectly for the big quilts. i avoid triangles for Humanitarian, when i know someone will wash it on a rock in a 3rd world country! any scraps are great for the crazy quilts, etc. not much goes to waste.