I recently found a new brand of tee shirts that I simply LOVE LOVE LOVE. You can find them at Buckle and other stores, though the selection there isnt always the best, and these are probably the most expensive tee shirts you will ever find. There are dozens of cool designs in all sizes on their website. While they are made of cotton, the material is thin and EXTREMELY comfortable. It feels as if you aren't even wearing anything. Oh ya, they make some pretty cool shirts for women too!
Check out their web site:
Aqua Vi Shirts