The WordPress user profile comes with the ability to add social network IDs for AIM, Yahoo IM, and Jabber/Google Talk. However, most of those networks or either dead or dying. So what if you want to add Twitter, Facebook, Linkedin or other more popular social networks to your user profiles?
ThemeFuse Extend User Profile is the answer. This plugin comes with fields for social network links, but you can also add more and create custom profiles for your users.