There is a $10 sale now on at threadless - for those of you who have never heard of them, this is an excellent US based T-shirt company. I have ordered from them before, and the quality of the items is excellent, and the designs are unique.
The only thing to watch out for is the customs charges - but you won't have an issue if you keep your order to 3 t-shirts or less. For example, I have just ordered 3 tees at a cost of $39 delivered, which is about £6.50 per tee.
P.S. We generally do not allow non-UK companies on HUKD, but this company is now allowed - see the comments forum thread for more discussion on this.