Just a little gem I found on the web for saturation from http://www.klanghelm.com/IVGI.html
Just used this on a mixes vocal track and I really like the subtle soft clipping distortion this provides.
it’s got nice dynamics, transparency and adjustable harmonics.
Definitely one to consider using on your tracks to add a little ‘mojo’ to vocals.
UPDATE: 1st August 2013:
I’ve also used this plugin on guitars, bass, drums and full mixes with excellent results. Try and see for yourself!