Chronic Dev Team has released the GreenPois0n jailbreak tool for the Mac OS X now and you could download it from their official site. Earlier they released GreenPois0n for Windows first and then for Linux and we reported about those. You could use it to jailbreak iPhone 3GS/4 and iPod Touch 3G/4G on iOS 4.1 and iPad on iOS 3.2.2 on Mac OS X.
We have already posted the jailbreak guide for GreenPois0n. Follow that guide given here to jailbreak your device.
Download GreenPois0n for Mac OS X from here.