For AppleTV 2G users, the goal is for PwnageTool to cover you by Funday/Sunday (but still very limited app capability).
This upcoming version of PwnageTool will be based on Geohot’s Limera1n bootrom exploit. It will allow you to jailbreak your iPhone on iOS 4.1 with a custom firmware that won’t change your phone’s baseband. This will, consequently, allow you to use Ultrasn0w to unlock the phone and use it with a carrier of your choice.
Developer iH8sn0w previously confirmed that Sn0wbreeze 2.1 (think: PwnageTool for Windows) will be pushed out a few days after PwnageTool is released. So, keeping that in mind, the next version of Sn0wbreeze should come some time after Sunday.