i go to old navy for that, most shirts donw fit me well because im pretty big up top and small waist so they look funny. The old Navy T-shirts are like 5 bucks, and they fit well
EBay's good for t-shirts - just search by brand name. Some styles are on there all the time at good discounts. I've gotten brand-new Quiksilver at half the mall price, both s/s and l/s.