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