I've made a number of t-shirts for myself using these guys:
http://www.zazzle.com/cr/home
It's the only company I could find that didn't require a minimum order of 5 or more. Just "borrow" the artwork you want to use to your computer desktop, go to the menu that lets you position the artwork on the shirt & voila.
They're really good Haynes shirts & the total cost is about $20 apiece.