Calibre is the giant of ebook management, and this app is the perfect (ahem) companion for it. With just a few clicks, you can add any book from your computer to your eReader over USB or Wi-Fi. You can also store your ebooks on the cloud for easy access from wherever you are. What's so surprising is how well it works, and how easy it is to use. If you've got a lot of ebooks and are ready to cast off the shackles of Amazon, this is the app for you.
Mood Messenger is one of the youngest apps on our list. It doesn’t have a million and a half features, but that’s one of the nice things about it. Mood Messenger keeps things simple while still offering the key features you’ll want. Mood Messenger users can also send messages to each other without using SMS. The app is completely free with no in-app purchases. Droid App