Continuing the focus on free dither plug-ins, Airwindows has released TapeDither and SpatializeDither for Mac OS X and Windows in AU and VST plug-in formats.
TapeDither is a TPDF variant with noise like reel-to-reel tape.
YouTube.com/watch?v=MNUQ8itfw2I
SpatializeDither is a spatial positioning and clarity dither.