After focusing quite a bit of energy on the iPod and notebook computer accessory markets, the last year or so has been a quieter period for Targus: it all but sat out the second-generation iPod nano and shuffle, and we haven’t seen much for full-sized iPods or MacBooks either. This week, the company returned to its strengths in the laptop bag market, unveiling three new water-resistant Radius series cases for the Apple MacBook and 15”…