All these codes are collected from different sources in the internet. I have tested only some of them. Some of these may not work on all models. So, please try at your own risk.
Software version : *#9999#
IMEI number : *#06#
Serial number : *#0001#
Memory capacity : *#9998*246#
Debug screen : *#9998*324# or *#8999*324#
LCD kontrast : *#9998*523#
Vibration test : *#9998*842# or *#8999*842#
Ringtone & alarm test : *#9998*289# or *#8999*289#
Smiley : *#9125#
Software version : *#0837#
Display contrast : *#0523# or *#8999*523#
Battery information : *#0228# or *#8999*228#
Memory capacity : *#8999*636#
SIM card info : *#8999*778#
Date & alarm clock : *#8999*782#
Display during warning: *#8999*786#
Hardware version : *#8999*837#
Network info : *#8999*638#
Show Received channel number & received intensity : *#8999*9266#
Software Version : *#1111#
Firmware Version : *#1234#
Hardware Version : *#2222#
All Versions : *#8999*8376263#
Test Menu : *#8999*8378#
GPSR Tool : *#4777*8665#
LCD Brightness : *#8999*523#
Error LOG Menu : *#8999*377#
EEP Menu : *#8999*327#
Debug Mode : *#8999*667#
Phone Model {Wap} : *#92782#
JAVA Mode : #*5737425#
Call List : *#2255#
Bluetooth MAC Adress : *#232337#
Java Version : *#5282837#