I've had
a store on Zazzle for a little while and it's earned me a bit of cash - the profit margin on Zazzle shirts isn't great, but since they're doing all the printing and distribution then perhaps that's to be expected. You can always set your own price if you really want to make more per shirt, as long as it covers their printing/supply fees.
From what I've heard back the print quality is also very good, especially for a print-on-demand supplier.