CafePress.com

I placed my order on Saturday, they sent me shipment confirmation on Sunday, and it arrived on Wednesday. I was skeptical, but everything looks great!
The only complaint that I have is that the tee-shirt was a really strange size... the arm holes were lower than they should be and the shirt didn't fit quite right.  I was given a prompt refund.
The print quality on the shirt is great, though.
I also ordered magnets and ceramic ornaments. Adorable! I will definitely order again.

Update- they've changed aspects of the site and their customer service has gone downhill over the last few years.  Deals are scarce and prices are doubling.  I'm reconsidering whether I will order from them again.

I wanted to comment on the excellent customer service I received from cafepress.com. I had ordered a t-shirt for my 17 mo old daughter. I received the shirt on a Wednesday and while it was good quality, I was disappointed because the color of the print on the shirt was not the same as pictured on the website or in the text description of the shirt (it was supposed to be hot pink and was more of a khaki). I called the customer service number on my receipt and a very nice young lady apologized, helped me order the shirt in a different color combination, and even suggested I try the shirt on my daughter to make sure it fit (I actually decided to go one size larger). She assured me there would be no additional charges. When I asked how I was to send the first shirt back, she said "keep that shirt as a gift from cafepress.com". While it is not exactly what I had wanted, it is still a cute and perfectly useable shirt. The second shirt arrived on Friday of the same week and it is great!

My order was shipped the day after it was ordered and I received it 5-6 days later. However, the order was printed incorrectly and I had to contact customer service. I received a response within hours and it was beyond my expectations. Not only did they send a replacement order right away, they told me to keep the defective item because they did not want me to incur any charges sending the item back. I am extremely thrilled with their customer service and will be using them again in the future.