Fat Free CRM - Merge Contacts and Accounts
This plugin provides functionality to merge duplicate contacts and accounts.
When you hover over a contact or account, you will see a 'merge' link next to edit and delete. Type in a part of the name of the account or contact, and click the one that matches. You will see a form with radio buttons, where you can choose the attributes that you want to keep or overwrite. There is also a "Duplicate <==> Master" link in the top left corner, if you need to reverse which one is merged into the other.
A merge will move all attributes from the duplicate to the master, including all notes/emails/opportunities/contacts/etc.
Copyright (c) 2010 Nathan Broadbent, Crossroads Foundation, released under the MIT license