Smartr: Unite Twitter, Facebook And More With Your iPhone Contacts

Automatic. Finds all the people you know from your email, calendar or social networks.
Personal. Puts a face to every name and email address.
Insightful. Detects and assigns phone numbers automatically.
Socially aware. Integrates Facebook, LinkedIn and Twitter.
Relevant. Ranks contacts by importance, so the most important people are at the top.
Fast. Search by first, last, company name or phone number to find anyone.
Contextual. View email and calendar subjects for each person.
Convenient. One click access to SMS, call or email.

(Source: cultofmac.com)