If you go to missouristarquilts.com she features in one of her tute's a great ruler that makes yards of binding from just 1/2 yard of material. I bought the ruler and it works great. Give me one second and I'll find the name of the ruler for you.
Ok it's the Simpli-Ez Bias Ruler by Susan Brown and it's super easy to use and makes bias from 1/4 all the way up to 2 1/2 inches. The video on the website for Missouri Star Quilts shows the super easy method for using.
http://tutorials.missouriquiltco.com/last.php