So, I designed a t-shirt that I wanted, and was thinking about ordering it when I looked at the price, and changed my mind.
A single black t-shirt with only a single piece of plain text on it (the most basic shirt you could get) was $40 ($AUS) plus $7.50 postage. However, one of the shirts I designed on CafePress (plain black t-shirt with my own graphic on it) is listed on the site at $23.99 ($US) and they charge $7 postage for the first item (successive items are cheaper). $30.99 ($US) is less than $36.50 ($AUS) so if I want any thing like that it's actually cheaper to design them up on CafePress and get them that way.
So, as a result I am planning on doing a CafePress run in the near future. My CafePress is at http://www.cafepress.com/randomreality, and there are lots of other CafePress stores with lots and lots of nifty items so have a look around and let me know if you want anything. Be aware that multiple items bought from different CafePress shops count as a single order for the purposes of postage.
Also, if you have any basic custom designs I can probably make them myself. Anything that requires real artistic ability will need additional help that I can't provide. :)