Yes, it’s Free Download of Angry Birds Rio today. Amazon is offering Angry Birds Rio free for few hours from their recently launched appstore. To begin you need to enable  “Debugging Mode” to initiate the installation.  Download Side Load Wonder Machine. Once you’ve downloaded it go to the amazon appstore and download their app for their appstore. To install this use the Side Load Wonder Machine (search youtube videos for tutorials). Then download the Angry Birds Rio. A message prompting unable to install app will popup in the screen.

Browse to “android\data\com.amazon.venezia\cache” in your AT&T android device. You should be able to find an “*.apk”  file in that location. Again using SWM install Angry Birds Rio. This approach should let you install any apps from Amazon which is not currently approved by AT&T.

Bingo! You’re now able to install Angry Birds Rio in your Samsung Captivate.

Edit: You can follow same procedure to install any free apps from amazon store, for e.g  Amazon has already offered Shazam and Swiftkey for free, both of which can be installed via side-loading through SWM.