The Australian Parkour Association has classes running in all the State capitals. Instructors run the sessions for love not money, so the fee for a 2 hour session is only $10 - an amazing bit of value when you think of how much a personal training session can cost. Be prepared though. This sport is not for the faint hearted or the brittle boned.
Go in loose comfortable clothing, not boardies or lycra. Wear shoes with a plain sole, like Dunlop Volleys and take a bottle of water. Instructors will make sure you are warmed up and then it is off to the hardest workout you will get this side of the SAS.
Crawling quadrupedal up a hill, leaping from heights and learning to tuck the momentum into a parachute roll and dive rolling through playground equipment are all things you can look forward to - and that is just on the First Timers course!