How to stencil a t-shirt. →[More:]This is a down and dirty (in the literal sense, like a cornucopia) tutorial on how to stencil your own t-shirts. I can vouch for the fact that it works. I pretty much follow her tute to the t except that I use a little foam roller instead of a brush. The basic gist is that you draw something freehand on cardstock, or you find a great illustration online and enlarge it and print it out on cardstock, cut out the outlines with an exacto knife, and then paint it onto a shirt. Warning: stencilling your own t-shirts is an addiction.
They make great gifts, too. And imperfections just make them better, so don't worry about them.