What are your favorite free audio units?

This question is for those of you who may do some audio editing like myself. I personally use Amadeus Pro, which I find to be absolutely awesome. I had forgotten just how much I enjoy editing on the mac. Anyway, I am looking for free audio units to add effects or just make vocals sound better. Most of my jobs are small, like station ids, program promos, etc. But I get sick of hearing my own voice as is all the time, so if there are tools out there to spice things up a bit, that would be awesome.
Feel free to share your favorites. I think audio units work best for Amadeus, though if I'm not mistaken it can also handle vat.
Thanks in advance for your input.