Have you heard of freezer paper stencils? They are just about the coolest thing ever! I've seen them around all over the blogging world and just recently had the chance to try them out.
How it works, is you trace your design on the plain side of the freezer paper and use a Xacto knife to cut it out. Then you iron the freezer paper onto your piece of clothing, shiny side down. After making sure all the edges are ironed down well, you fill in the stencil with paint. Fabric paint gives the best result, but acrylic craft paint works pretty well too. When the paint is dry, you peel off the freezer paper and that's it!
I used a freezer paper stencil to create this shirt for my son's school fundraiser at school, Race for Education. I think it turned out really well, and he'll look totally cool running to help raise money for his school!