A friend and I built a t-shirt site too. It's so incredibly basic (ours is ugly) but was fun to do to actually write some software for the web (we arent really web guys).

The code is actually really cool because we never have to touch a shirt. Shirts.io handles all the t-shirt fulfillment, stripe handles payments, and we design shirts and add them to the site. If you don't have a t-shirt company, you should, just because it's cool to write a program that turns your own money into tshirts.

The site I made was www.binarytees.in