Asplenia Studios sells merchandise through Print-on-Demand (PoD) services. Essentially, you go to the webstore, choose a product, and they print it and send it off to you. On the down-side I get a smaller profit than if I was doing it myself but, on the plus-side I don’t have any overhead as they manage it all. I currently use two services, as described below (and would love any feedback on quality issues):

Teepublic – Teepublic is great if you live in North America. They tend to have regular sales on all items, and feedback seems to indicate that their printing quality is good. On the flipside, shipping costs are quite steep (although ordering multiple items cuts that quite a bit), and international shipping is also quite high.

Redbubble – Redbubble is a new store I am trying out. The biggest benefit is that they work internationally. Just click on the link and you will be sent to the webstore for your country. Prices can be higher than Teepublic unless they are running a sale, which seems to be less frequent. I also haven’t had any feedback on print quality yet.