More than just a free photo-enhancement app for Android, Instagram connects its users to a photo-based social network that's more than 30 million users strong. With this powerful social functionality, the app makes it incredibly easy to not just polish and share photos, but also to keep tabs on friends through the built-in Instagram photo stream.
Start by signing up for Instagram with an e-mail address, username, and password. From there, you can link your account to your Twitter, Facebook, Foursquare, and Tumblr accounts. But don't worry, whenever you snap a picture, Instagram will still ask you which account(s) you want to share with. Linking just makes it so you don't have to log in every time. If you choose not to share with any linked accounts, then your photo will simply live on your Instagram profile, and will be pushed out to your followers' Instagram feeds.