Entertainment Earth just added new Firefly, Doctor Who and Dr. Horrible T-shirts -- including the shirt I've been meaning to get forEVER! (look up and don't mock me. I was always working at SDCC ;p )
Here's why I'm telling you.
Entertainment Earth is having a t-shirt sale and for every 3 shirts you buy, you get the 4th free. It doesn't matter if they're in stock or pre-order. There's no "US only restriction". It's just buy 3 and get the fourth free. There's close to 600 shirts at last count, so I'm guessing there might be a few that would make your holiday shopping easier.
It's only till November 8th, tho, so if you're gonna do it, I suggest you get on it.
Plus, cause I just...I.../swoon...
Sale link in case you missed it up top. ;-)