The e-reader battle is heating up. Two days ago, Barnes & Noble fired a shot across Amazon’s bow with their gorgeous new Nook e-reader. Today, Amazon announced free Kindle software (similar to their excellent iPhone app) for any PC with the new Windows 7. Better yet, as Gizmodo points out, if you have a multi-touch tablet laptop, you’ve suddenly got a full-color Kindle, too. [Gizmodo]