I'm still catching up on the "sea of bulletin board", and found another scrap pinned to the mess:
Custom t-shirt printing by http://skreened.com/
If you need just a couple of t-shirts for employees, a trade show, a test run, or even if you just like the idea of having t-shirts printed up but you don't need dozens of them, this looks like a pretty good resource. I haven't printed shirts with them (and would be curious to hear about print quality if you have), but it looks like they have a good variety of shirts available, and it looks like ordering might not be too difficult.
Other shirt vendors I've tried include:
Cafepress.com: Decent print quality, but I'm not thrilled with the shirts available.
Zazzle.com: Better shirt selection, but I don't love their ordering interface (at least not on my Mac)…
Got a great short-run shirt vendor that I should know about and try out? Let me know about it in the comments…