Developed based on the needs of studios using more than one DAW application, Asylum Studio Productions have created a free plug-in that allows fine tuning of pan law and other panning characteristics for both mono and stereo tracks.
The initial release supports both AU and VST and is Universal Binary. RTAS and Windows support is scheduled for later this year.
Using various curve algorithms for both the pan law and channel attenuation, along with a very detailed graphical representation of the pan settings, a user can very quickly relate what they see to what they hear. This is very useful since most DAWs do not give you many options to control how the built in panners work.