Also explained here: iOS: How to transfer or sync content to your computer
To sync contacts with your computer, choose "Sync Contacts with" within iTunes for Windows, or "Sync Address Book Contacts" on your Mac.
You can sync your contacts with:
- Microsoft Outlook 2003, Microsoft Outlook 2007, Microsoft Outlook 2010 (Windows XP, Windows Vista, or Windows 7)
- Windows Address Book (Windows XP)
- Windows Contacts (Windows Vista / Windows 7)
- Address Book (Mac OS X)
- Microsoft Entourage 2004, Microsoft Entourage 2008, or Microsoft Outlook 2011 for Mac
Note: If using Microsoft Entourage, use Microsoft Entourage 2008 12.1.2 or later if syncing with Mac OS X v10.6 or later. If you would like to sync data on your Mac with Entourage, enable syncing between Entourage and Address Book.
This way the contacts will be copied to Windows Contacts that I tried once, but found quite complicated in its way of handling groups and contacts in general. I have therefore been looking for a solution to edit my contacts on the PC and simply export all of them to an external hard drive once they're clean. There are not many apps out there, but the easiest one that I found is called iPhone Contacts Backup.... It's still a beta version and I had to share and like on Facebook and Twitter to be able to export all of my 140 contacts. But, once I was done with sharing, it took only some seconds to back up my contacts. Definitively a very useful app for iPhone users who are trying to mange their contacts on PC.