I do my fluids quite often as I need the car to be reliable and I track it alot.
Oil - 5000
Oil Filter - 5000
Fuel Filter - 10000
Brake Fluid - Every few track days or once a year. If you cant remember when you last did it then its been to long.
Coolant - Once a year
Gearbox Oil - Once every 18 months for me, but you can get away with once every 30,000k's or more
Diff Oil - Once every 18 months again but you can get away with once every 60,000
Ignore the manual guys. Its full of lies, it says you dont have to do the Diff Oil but my god you should have seen the crap that came out of my one when we did it. It was putrid, you should definatly change it to keep your LSD working nicely.