George Hotz, who was the first to unlock the original iPhone, has released a tool that will allow users to jailbreak the iPhone 3GS. The application itself is very small, less than that of a C++ hello world program. The application is called purplera1n, and requires nothing more than a few clicks to jailbreak the phone. If your jailbroken state somehow gets corrupted, the purplera1nyday files will allow you to get back to that state with a few simple tools. Jailbreaking will allow the users to install third party applications that haven't been approved by Apple, but won't allow for using the phone on any network.