Amazon has launched their long-awaited Appstore, which will provide another avenue for users to download Android apps from. There's one problem though: AT&T users cannot yet access it due to the carrier's restriction on 3rd party app downloads.
Amazon has listed that they are working with AT&T on a solution that will allow users to download the app, but as of right now, it is restricted.
Until then though, we still have our Sideload Wonder Machine, which still allows the installation of 3rd party apps on carriers *cough* AT&T, who restrict users from choosing to download 3rd party apps. [Amazon.com/appstore]