They are FANTASTIC! I use the ones made from SHOUT. They are by the fabric softener sheets in the laundry aisle normally.
Basically you throw a sheet in with you wash and it catches any dyes that come out of your clothes. Because I don't prewash my fabric I always use them.
With all the white in this quilt I didn't want the white to come out pinkish or blue-ish. :)