Here is a list of my most used apps on my iPhone.
The Facebook app allows users to update their status, write on a friend's wall, or view and comment on certain pictures, and much more on this easy-to-use app.
If you are a Twitter user, Tweetbot is a great alternate from the official Twitter app. It runs very smooth, and does much more than most Twitter apps. My only problem with this app is that it is costs $2.99 and isn't free like most other apps.
Instagram is my default camera app. This free app allows you to take crisp clean pictures on your phone, then apply several effects to the picture to make it darker, brighter, or by adding unique borders to your photo. Finally, after you are satisfied with your picture, you are allowed to upload it direct to Facebook, Twitter, Tumblr, or Flickr based on your preference.
Spotify is a free music application that allows users to search for any song or album to stream directly on their phone. Although it requires membership after a thirty day trial, it is well worth it. I use Spotify to add and create playlists of my own music on my computer. Finally, Spotify also allows users to automatically post what they are listening to on Facebook if they want that option.