Vistaprint offers a Custom Printed T-Shirt for $12. Coupon code "VPSHIRT25" cuts the price to $8.99. With $4.99 for shipping, that's $3 off list and the lowest price we could find, although we saw it for $2 less last week. Only front printing is included in the price; additional customization is available for an extra cost. It's available in sizes S to L.
Note that the coupon may automatically apply in cart.