Edit Linked Library

Overview
Select an object that's been linked from a separate .blend file. In the 3D View's Toolshelf, the Edit Linked Library panel will show a button labeled "Edit Linked Library". Click this button to open the .blend file that the active object is linked from. Once you complete your work to the linked file, return to the Toolshelf and click the "Return to Original File" button.

By default, this addon automatically saves your current file before opening the linked library or returning to the original file. This can be disabled using the Autosave toggle in the Edit Linked Library panel of the Toolshelf.