[Galaxy Tab General] pakalrtb:
Found these codes from a Galaxy S forum but most if not all of them will work for the SGT as well.

*#06# (Display IMEI number)

*#1234# (Display current firmware)

*#*#4636#*#* (Diagnostic and general settings mode)

*#*#7780#*#* (Factory soft reset)

or *#7780#

*2767*3855# (Factory hard reset to ROM firmware default settings)

*2767*4387264636# (To display product code)

*#272*imei#* (Display/change CSC code)

or *#272*HHMM#*

*#*#1472365#*#* (GPS test settings)

*#*#197328640#*#* (Service mode main menu)

*#12580*369# (SW & HW Info)

*#0228# (ADC Reading)

*#32489# (Ciphering Info)

*#232337# (Bluetooth Address)

*#232331# (Bluetooth Test Mode)

*#232338# (WLAN MAC Address)

*#232339# (WLAN Test Mode)

*#0842# (Vibra Motor Test Mode)

*#0782# (Real Time Clock Test)

*#0673# (Audio Test Mode)

*#0*# (General Test Mode)

*#2263# (RF Band Selection)

*#9090# (Diagnostic ConfiguratioN)

*#7284# (USB I2C Mode Control)

*#872564# (USB Logging Control)

*#4238378# (GCF Configuration)

*#0283# (Audio Loopback Control)

*#1575# (GPS Control Menu)

*#3214789650# (LBS Test Mode)

*#745# (RIL Dump Menu)

*#746# (Debug Dump Menu)

*#9900# (System Dump Mode)

*#44336# (Sofware Version Info)

*#0289# (Melody Test Mode)

*#2663# (TSP / TSK firmware update)

*#03# (NAND Flash S/N)

*#0589# (Light Sensor Test Mode)

*#0588# (Proximity Sensor Test Mode)

*#273283*255*3282*# (Data Create Menu)

*#273283*255*663282*# (Data Create SD Card)

*#3282*727336*# (Data Usage Status)

*#7594# (Remap Shutdown to End Call TSK)

*#34971539# (Camera Firmware Update)

*#526# (WLAN Engineering Mode)

*#528# (WLAN Engineering Mode)

*#7412365# (Camera Firmware Menu)

or *#*#34971539#*#*

*#80# (Unknown)

*#07# (Test History)

*#3214789# (GCF Mode Status)

*#272886# (Auto Answer Selection)

*#8736364# (OTA Update Menu)

*#301279# (HSDPA/HSUPA Control Menu)

*#7353# (Quick Test Menu)

*2767*4387264636# (Sellout SMS / PCODE view)

*#7465625# (View Phone Lock Status)

*7465625*638*# (Configure Network Lock MCC/MNC)

#7465625*638*# (Insert Network Lock Keycode)

*7465625*782*# (Configure Network Lock NSP)

#7465625*782*# (Insert Partitial Network Lock Keycode)

*7465625*77*# (Insert Network Lock Keycode SP)

#7465625*77*# (Insert Operator Lock Keycode)

*7465625*27*# (Insert Network Lock Keycode NSP/CP)

#7465625*27*# (Insert Content Provider Keycode)

Secret Codes- Some of these will only work with specific firmware

*#06# (Display IMEI number)*#1234# (Display current firmware)

*#*#4636#*#* (Diagnostic and general settings mode)

*#*#7780#*#* (Factory soft reset)or *#7780#

*2767*3855# (Factory hard reset to ROM firmware default settings)

*2767*4387264636# (To display product code)

*#272*imei#* (Display/change CSC code)or *#272*HHMM#*

*#*#1472365#*#* (GPS test settings)

*#*#197328640#*#* (Service mode main menu)

*#12580*369# (SW & HW Info)

*#0228# (ADC Reading)

*#32489# (Ciphering Info)

*#232337# (Bluetooth Address)

*#232331# (Bluetooth Test Mode)

*#232338# (WLAN MAC Address)

*#232339# (WLAN Test Mode)

*#0842# (Vibra Motor Test Mode)

*#0782# (Real Time Clock Test)

*#0673# (Audio Test Mode)

*#0*# (General Test Mode)

*#2263# (RF Band Selection)

*#9090# (Diagnostic ConfiguratioN)

*#7284# (USB I2C Mode Control)

*#872564# (USB Logging Control)

*#4238378# (GCF Configuration)

*#0283# (Audio Loopback Control)

*#1575# (GPS Control Menu)

*#3214789650# (LBS Test Mode)

*#745# (RIL Dump Menu)

*#746# (Debug Dump Menu)

*#9900# (System Dump Mode)

*#44336# (Sofware Version Info)

*#0289# (Melody Test Mode)

*#2663# (TSP / TSK firmware update)

*#03# (NAND Flash S/N)

*#0589# (Light Sensor Test Mode)

*#0588# (Proximity Sensor Test Mode)

*#273283*255*3282*# (Data Create Menu)

*#273283*255*663282*# (Data Create SD Card)

*#3282*727336*# (Data Usage Status)

*#7594# (Remap Shutdown to End Call TSK)

*#34971539# (Camera Firmware Update)

*#526# (WLAN Engineering Mode)

*#528# (WLAN Engineering Mode)

*#7412365# (Camera Firmware Menu)or *#*#34971539#*#*

*#80# (Unknown)

*#07# (Test History)

*#3214789# (GCF Mode Status)

*#272886# (Auto Answer Selection)

*#8736364# (OTA Update Menu)

*#301279# (HSDPA/HSUPA Control Menu)

*#7353# (Quick Test Menu)

*2767*4387264636# (Sellout SMS / PCODE view)

*#7465625# (View Phone Lock Status)

*7465625*638*# (Configure Network Lock MCC/MNC)

#7465625*638*# (Insert Network Lock Keycode)

*7465625*782*# (Configure Network Lock NSP)

#7465625*782*# (Insert Partitial Network Lock Keycode)

*7465625*77*# (Insert Network Lock Keycode SP)

#7465625*77*# (Insert Operator Lock Keycode)

*7465625*27*# (Insert Network Lock Keycode NSP/CP)

#7465625*27*# (Insert Content Provider Keycode)