At first hearing it sounds like something straight of Snow Crash: researchers at the University of South Carolina took a cotton t-shirt, treated it with boron, and ended up with a fabric reinforced with nanowires made of boron carbide -- a material used in tank armor.
Sadly, a bullet-proof t-shirt is probably some ways away yet. But the technique produces a strong, light material that could be used not only in body armor but in the manufacture of lightweight fuel-efficient vehicles.