There is a place in Terre Haute, Indiana, called Sycamore Sun and Spirit; their website is
www.greekshoponline.com and is an excellent source for shirts and other gear. They are a smaller family-owned shop, but they have a quick turn-around and do custom designs. They are used to doing shirts and other Greek gear for two local colleges, so they have lots of experience with Greek organizations and know their colors, symbols, etc.
What I like the best is that they have local artists that they work with. So, for example, if you have an idea but no real design, they will take what you give them, have their artist sketch up sample designs, and e-mail them to you. This way--if you are working on a rush shirt during the summer--the final design can be e-mailed to the rush chair and whoever else for final approval. You also won't end up with some design that appears in a catalog that you see coming and going on every campus.
Their prices are VERY good---the more shirts you order, the better the price. And--they will tell you up front about the shirt quality. The group I work with has had their designs used for several years, and the shirts have NEVER faded. It's funny to see seniors wearing their freshman year rush shirts that still look almost new!
They do a great deal of on-line work as well as in their own store. I will say I know a couple groups who have gone on-line with the "big" companies have had errors and cheap shirts and have gone back to Sycamore. They have done many, many of the national groups as well as back-to-school Panhellenic and IFC rush shirts. They also do pledge class shirts or sweats if you use those. I guess what I really appreciate is their quality and perfection. Before anything goes to the screen printer, they have the group take a final look on-line and approve the printing---your "big" companies will not usually do that.