I came across a great site for t-shirt designers looking to make a penny or two. It's called Qwertee and if you're familiar with sites like TeeFury and The Yetee it works the same way with one exception. Like the sites mentioned if your design is selected you grant them the right to sell your design for 24hrs. In return you get $1 for every shirt sold. The one exception about Qwertee is the designs are selected by fellow designers and members of Qwertee. You can also see how many votes it's getting which can be a little addictive checking every hour to see if it's got anymore.
I've currently got a design up for sale now. Take a look and maybe buy yourself a tee. Alternatively submit a design and see how it goes!