Caulk another one up to the comeback kid. Palm, in the middle of its huge turnaround, has announced the general availability of a unlocked GSM Centro.

Palm announced that the popular Palm® Centro™ smartphone is now available unlocked for U.S. customers. Now offered on Sprint, AT&T and Verizon Wireless – the nation’s three largest carriers – and in an unlocked GSM version, Centro gives U.S. customers the ability to choose the mobile phone that’s right for them.(1) Palm also announced that Google™ Maps for mobile with My Location on Centro is available for Centro starting tomorrow, giving customers faster access to local maps and driving directions.(2)

The unlocked Palm Centro retains the smartphone’s compact, modern design and is dressed in a new white color with grey accents. Centro offers customers more choices to stay in touch with friends, family and co-workers by using voice, text messaging, email or the web. Also available in 25 countries worldwide, Centro is Palm’s smallest and lightest smartphone to date.

Google Maps for mobile with My Location makes it easier and faster for Centro customers to get mapping and direction information by approximating the user’s current location on the map. This saves time and keystrokes for people trying to find where they are, what’s around them, and how to get there.

The revamped Google maps application is available today, and the device is available for $299.