How to back up the address book? I want to wipe the phone clean (or reset it, not sure about the nomenclature).  Meaning, I'd like to get rid of all the apps, all the data, everything.  Except for the contacts.  I'd like to somehow restore them after wiping the phone.

So I know there is an option to go to Settings/Privacy/Factory data reset, which wipes it clean (i assume), and that is what I am planning to use.

I also see an option to Back up my data in Settings/Privacy.  However, this option backs up all the application data, passwords, etc... as well to Google servers.  But, again, I only want the contacts.

So, is there a way to do what I want?

For reference, this is a Nexus One with Android 2.3.6.
Your contacts are automatically backed up to the Google account you set up your phone with.  So long as you have the "Contacts" sync setting on, any changes you've made to your contacts should be mirrored in your Gmail contacts online.  After you wipe your phone, if you use the same account to set it up again the contacts will automatically download on the first sync.

You can verify that your contacts are backed up by going online to Gmail, clicking on "Contacts", and checking them against your phone's address book.