Dave Jewell - Reverse Engineering Apple's OS X
Summary: "With all these tools in your arsenal, reverse engineering Cocoa executables is actually very simple. In fact, it's a good deal more straightforward than most Windows executables."
The tools are IDA Pro, class-dump, class-dump-x, otx, and his own utility which it doesn't look like he's released. I guess you need to keep a discriminator proprietary.
IDA Pro: http://www.hex-rays.com
Class-Dump: http://homepage.mac.com/nygard/Projects/index.html
class-dump-x: Just search online, and you'll find it.
Read more about class-dump at http://www.cocoadev.com/index.pl?ClassDump
otx: http://otx.osxninja.com/
Bundled with OS X: lipo, ditto, otool
This article is at http://www.theregister.co.uk/2009/03/17/mac_secrets_reverse_engineering/print.html
He's written several other article about reverse engineering or undocumented components at the same site.
