n spite of Apple's grumbling, Amazon's proceeding full steam ahead with the rollout of its Appstore for Android. The switch has just been flipped and early adopters will be welcomed with a free copy of Angry Birds Rio, whose Android launch Amazon scooped all to itself. Beyond day one, Rio will be a $0.99 app, but others will take its place as the online retailer is aiming to serve one usually-paid app for free each day. A total of around 3,800 applications are available at launch and you'll be able to get on board via either a dedicated Appstore app on Android (sideload link available below) or Amazon's web interface. The latter offers you a 30-minute Test Drive facility, where you can try out a program you might fancy for your phone before purchasing. Service looks to be US-only for now -- sorry, international users.