latest official OS can be found by sprint. Its 4.5.0.175 i believe
There's also an "Unofficial" OS version 5.0 (which i'm running with a hybrid) that works ok. You can find both on these forums. just search 83xx forums and you'll find it. if all else fails.....GOOGLE!
hope that helps
edit: ok he beat me to the punch-line but whatever helps!