Rockerby 

See who else is editing the same content as you! An Umbraco package to help prevent content overwriting by multiple users.

Impersonator for Umbraco lets administrators impersonate other users

Enhance Umbraco's rollback functionality with visual rollback previews. This extension builds ontop of the existing Umbraco Rollback modal and allows for the JSON diff to be viewed as well as the visual diff.

A flexible, draggable link picker for constructing site navigation menus in Umbraco