Griffin Technology today announced that its iClear and Disko cases are now available for the second-generation iPod nano. The iClear case ($20) features a two-piece shell design with crystal-clear polycarbonate protection. It offers screen protection and has an opening for the click wheel. The Disko case ($30) senses movement and responds with colored lights that blink and flash in moving patterns around the click wheel. The Disko case comes in black and clear. Both cases will be available in stores for the holidays.