Woot.com is a group of (American) sites which are a bit like CatchOfTheDay - one day, one deal type things.
The only one I've ever used is http://shirt.woot.com and I have to confess a huge love for it :) They sell one t-shirt a day. Each week there's a competition on a particular theme and anyone can enter - the top 3 shirts get sold Fri-Sun. For the other days of the week, shirt.woot just comes up with its own prints. There's also The Reckoning for all the shirts whose days are up but remain in the top 20: http://shirt.woot.com/Reckoning/
T-shirts are very good quality, range from super-cute to gross and freaky, and are a bargain at US$10 + US$5 shipping to Australia.
I think half the t-shirts I own come from this store, and I'm pretty sure I'm going to acquire some more with this coupon!
They look nice. wish they had free shipping.