sure if this is as important as the jailbreak for the iPhone, but Andriod is now jailbroken and developers now have full system access. Although the G1 handset has far less limitations than the iPhone, we'll have to wait and see how big of a deal this really is.
The jailbreak was done thanks to a telnet application called PTerminal which allows you to telnet into the G1, and as such get access to the command line interface of the G1. As of right now, this doesn't mean a whole lot, but then again, this was the case with the iPhone, as well, during the early stages of it being jailbroken.
If nothing else, this might lead to a free application for unlocking the G1, unlike the current way which is being charged for either by the network or by a Website who offers to unlock your G1 for you. As for any other developments, well, we're just going to have to wait and see what the community comes up with, but anything is possible in the long term.
More details here
Google G1 phone gets unlocked