Amazon Appstore for Android
Amazon has today made it's AppStore for Android live. You can access it from either your internet browser or by using it's Android app. You will have access to around 3,800 apps at launch, which will probably grow in the coming months as more developers starts putting their apps up.
You can sign into Amazon using your Amazon account which will track your purchase history and make suggestions based on it. Amazon will also offer a free app a day in an attempt to promote their store.
Amazon's Appstore also offers a test drive option, where you can try your app for 30 minutes in your browser before purchasing.