LinkedIn is free (iPhone). LinkedIn is a social network for finding business contacts, with more than 120 million registered users from 200 countries, representing 150 business sectors.
Twitter is free (iPhone, iPad). Read about what you care about: instant messages from your friends, experts, favorite celebrities, and the latest news from around the world.
Instagram – free (iPhone, iPad). Instagram is a free photo-sharing app that allows users to instantly apply different filters and frames to photos they’ve just taken, and share them through Instagram or through a variety of other social networks, including Facebook, Twitter, Foursquare, Tumblr, Flickr and Posterous.
Facebook is free (iPhone and iPad). The Facebook app allows you to stay in touch and share information with friends right on the go.
