Via Slashdot a couple days ago, I became aware of the Openmoko project, an attempt at an cell phone O.S. that's based on open-sourced software, like the Linux kernel, the GNU C library, the X window system, and the GTK+ toolkit. It seems that FIC is behind this, and has already released the Neo1973 for developers to pick up and start programming on (The wiki for the O.S. states that the software is still in a pre-alpha state and not ready for end-users yet).
This is a rather different approach than the "total-control" approach most other cell phone seem to take. Opening up the software source allows for the innovation that individual developers can afford to apply to problems. There's already features discussed like having the AGPS-enabled Neo1973 be able to detect its location and change modes depending on that information, such as going into silent mode when entering a theater. Or be able to transmit its location when it gets stolen.
The Neo1973 is currently available directly from the openmoko site in two packages:
Both are offered as developer previews. The Base is mainly for mobile application developers while the Advanced include items like a "developer boards" for a hardware hacker to play with.
FIC is planning on releasing consumer versions of the New1973 in october, according to this wiki entry at a cost of around $450 for the base system.
I think Centennial Wireless uses a GSM network, and I've been looking for a new phone to replace my beat-up Samsung model. I'll be keeping a close eye on the Neo1973 and the Openmoko project, even if I originally didn't have an interest in a smart phone otherwise.