Revo literally reached into space to design its newest line of sunglasses. Revo glasses use LMS technology, originally developed by NASA for satellite portals. For you down on earth, that means good protection from ultraviolet and infrared rays, and polarized lenses that cut down on bright reflections from shiny surfaces. These shades are also available with photochromatic lenses, which darken when exposed to sun rays and lighten in more shaded areas. The stylish and tough Slitty 3025 Flex, for instance, are great for those cloudy days when there's a lot of sporatic sunshine to deal with. They're so lightweight and comfortable (the flex hinges mean they hug your head lightly, but securely) that you'll even forget you have them on. Prices start at $189 for photochromatic sunglasses.