If you’ve ever lost all your cell phone contacts, you may already know you can easily track down a friend’s phone number by looking it up on Facebook. What you may not have realized is just how easy it is just to sync Facebook contacts with your phone to get all those contacts back.

So how can you sync your phone’s contact list with Facebook? If you have an Android 2.0 and up, it’s easy.

If your phone is running Android 2.0 or above, just install the native Facebook app. You will be given the option to sync your contacts automatically – you can choose to sync only selected or all of your contacts. You can also manage sync settings under the Settings panel.

Android automatically syncs Facebook contacts with your phone using the native Facebook app

If you have an iPhone or Blackberry, it’s a little more difficult.

If you have an iPhone or Blackberry, there’s currently no way to export your Facebook friends’ phone numbers or email addresses to your iPhone or Blackberry contacts. The Facebook app does show you people who have provided their phone numbers, and by clicking through the list you can see the friends who you can call using your iPhone or Blackberry, but there’s no integrated synchronization of contact info from Facebook to contact info in your iPhone address book.

There are third-party options that can assist with syncing your Facebook contacts with your iPhone. The app AddressBookSync works moderately well for the iPhone, and the GreaseMonkey extension for Firefox is a great tool for helping export Facebook contacts to your iPhone. The Facebook Blackberry app syncs names and photos, but there is no good way at this time to sync phone numbers.

One option for Blackberry users, though painful, is to sync Facebook contacts with a Yahoo account, and then export that contact list as a CSV file to your desktop. That file can then be imported to Google, and synced with your Blackberry.

And what about feature phones?

If you are one of the 79% of mobile phone users still using a feature phone, stay tuned – Facebook is introducing a native app for feature phones including LG, Nokia and Sony Ericsson phones. Facebook is promising that the native Facebook app for these feature phones will provide the ability to sync Facebook contacts.