even Andy of Sqawkbox can only find decodes for the UK, Turkey and another country that I've forgotten - so it wouldn't be much use for users in the rest of the world.
seems to be some info in these docs for Australia:
http://www.ivaoau.com/atc/index_ssr.phphttp://www.casa.gov.au/pilots/download/vfr/general.pdfmerged data for Australia:
0000 SSR data unreliable
0001-0017 Air Ambulance Emergency Medivac - Helicopter
0020-0027 Air Ambulance Emergency Medivac
0030-0037 Radar Flight Evaluation / Sector Calibration
0040-0057 MET research flight
0060-0077 Aircraft Paradropping
0100-0177 Royal Flights
0200-0277 Royal Flights - Helicopter
1000 NATO Fighter Ops.
1100 NATO Fighter Ops.
1200 Standard VFR in Australia
2000 Civil IFR flights in G airspace.
2001-2777 IFR Flights in Australia
3000 Civil flights in A, C & D airspace or IFR flights in G airspace
4000 NATO Fighter Ops.
5000 NATO Fighter Ops.
6000 Military flights in G airspace
7000 Standard VFR in Europe - In US. standard VFR code is 1200
7001-7017 Aerobactic flights
7020-7037 Police Flights
7040-7477 VFR flights
7500 Hi-Jacking
7501-7527 Aircraft engaged in police air support operations
7530-7557 Aircraft engaged in police air support operations - Helicopters
7600 Radio Failure
7700 Emergency
7701-7727 Aircraft engaged in actual SAR Operations
7730-7757 Aircraft engaged in actual SAR Operations - Helicopters
7760-7776 Ground Transponders Tests/Trials