There is one modifier that I do not leave home without, I always carry a large sheet of Ripstop Nylon. You would also carry a large bed sheet, I just think a sheet has to much weight.
With a large diffusion sheet be it a bed sheet or nylon fabric, you can shoot your strobes through it or even bounce you light off of it. In the photo above, I simply taped the nylon sheet to a window and shot my SB-800 through it. Soft beautiful light.
If your shooting inside where direct sunlight is streaming through a window, you can use this same sheet to diffuse that harsh light. I will often in narrow hallways, tape this sheet to the door frame of an office. Here is an older post regarding that use.
I mention here that I have a Small Strobes, Big Result workshop coming up this August 18th in Denver, for more information regarding attending click HERE. DT