If you have an iPhone on firmware 1.1.4 you're just dying to jailbreak and/or unlock, or an iPod Touch you want to liberate (and add apps to before June!), and you trust software created by 13-year olds(!), then iJailBreak may just be what you're looking for.
If you've previously used iJailBreak, you can update automatically. If you're new to the pirate scene and don't mind violating the ULA and your warranty, then this implementation is about as simple as it can get. Ars Technica reports you just download, install, run, connect, and viola!