Palmercash is offering 15% off everything in their store as part of their Independence Day sale. They have a bunch of shirts from various designers, with some of my favorites being Vintage Vantage, Heavy Rotation, and Ames Bros (the guys who made that Get Off t-shirt I just wrote about). With the 15% sale, you can get these shirts cheaper than buying directly from the designer.
No coupon is needed, the discount is taken when the item is added to your cart.
Check it out at Palmercash.