Got this from another forum
*#*#4636#*#* for battery and other general setttings like GSM/CDMA
*#*#8255#*#* for Gtalk service monitor
*#*#7780#*#* for factory data reset
*#*#34971539#*#* for information about phone camera (be very careful hitting options here)
*#*#7594#*#* change the "Power" button action in your phone.
*#*#197328640#*#* service mode
*#197238640# service mode
*#0*# testing mode
*#06# view IMEI number
*#1234# display phones current firmware
*#*#1472365#*#* gps test
i9000 Galaxy S codes
*#*#4636#*#* for battery and other general setttings like GSM/CDMA
*#*#8255#*#* for Gtalk service monitor
*#*#7780#*#* for factory data reset
*#*#34971539#*#* for information about phone camera (be very careful hitting options here)
*#*#7594#*#* change the "Power" button action in your phone.
*#*#197328640#*#* service mode
*#197238640# service mode
*#0*# testing mode
*#06# view IMEI number
*#1234# display phones current firmware
*#*#1472365#*#* gps test
i9000 Galaxy S codes