free au mac plug ins

Basically, you should just search KVR for freeware, Apple OS X, AU and then tell it to search for compressor or eq or limiter or delay or...etc. That is the best way to narrow it down. I honestly don't use AU because Cubase is VST only so I don't know of any other than the mda stuff, but KVR is a huge database that has all the info you need bro.

~006
 
AirWindows has some free plugins. At first glance - they may not look too impressive ... but once you have played with them, you'll hear that they in fact are very good tools to have in your bag of tricks.
Noodles already mentioned the CamelCrusher.
There are a few others out there as well.
Good luck.