The social networking site, Facebook, has a useful function [Friends>Find Friends].that allows you to import contacts from YahooMail, Gmail and Hotmail instantly. You just need to put in your email address and password. Then you can easily see who is already on Facebook and add them as friends. You also get an option to invite any of your other email contacts in one batch.
This is also possible to upload and scan an exported contacts file [CSV] from Outlook and AppleMail etc. They don’t provide the tips on doing it from LinkedIn, but it is very easy to export a CSV file from a link at the bottom of your LinkedIn ‘My Contacts’ screen.

