Amazon Appstore - The Amazon Appstore is a place to purchase and download apps for your Android device.
Mega - Secure File Storage and collaboration
Aptoide - Aptoide is a third party replacement for the traditional Google Play Store.
Dropbox - Online Sync and File Sharing
F-Droid - F-Droid is an interesting alternative for Android users who want to try something different and not have to use the Goole Play store all the time.
MediaFire - MediaFire is the simple solution for uploading and downloading files on the internet.