If you're looking for an ultra-low cost way to add style to plain dark shirts, sun bleaching lets you bleach basic designs using no more than cardboard, a few binder clips, and a week or two of sunshine.
Instructables user keynant came up with the process. Cut out your image on a piece of carboard and place it over the shirt. Place another piece of cardboard under the shirt and use binder clips to keep everything together. Place this outside in a sunny area for at least a week, and the contrast in the protected areas creates the design.
More details and photos can be found at the link below.
How to sun-bleach your own shirt [Instructables]