Previously, Chronic Dev Team released jailbreak tool Greenpois0n for Windows and Linux and now the Mac version of Greenpois0n is out there which provides an untethered jailbreak for iDevices running over iOS 4.1.
If your iDevice requires un-lcok then this is not recommended to upgrade to iOS 4.1.
Download Greenpois0n for Mac
Download Greenpois0n for Windows and Linux
Download Limera1n Jailbreak for iOS
Download iOS 4.1