Flux have released a new freebie plug-in called Stereo Tools for RTAS, AU and VST (Windows and OS X). Stereo Tool offers controls and visual feedback for the stereo stage.
From the Flux press release
Stereo Tool features ultra precise controls of input gain and individual pan for left and right channels. A phase inverter is available for each channel. A global stereo pan and a stereo width setting are also implemented to complete the management of the stereo signal.
Stereo Tool also offers an accurate visual feedback reflecting the signal content. A vector scope display, Peak meters for both inputs and outputs, and a phase correlation meter permanently monitor the signal.
As all Flux:: plug-ins it features 64 bit floating point processing, up to 8 FS (384 KHz).