This is one of many of my favorite things in my studio. It comes in different adhesive strengths, but I like the UltraBond the most. I order the mega roll (10 yards) from Amazon: here.
I use it layered between fabrics to make them stiffer, to repair/patch holes in clothing, and to add cool designs to fabric without having to sew, etc. Just iron and its done!
This product is awesome!