G'day Arnie, Sorcha and Jeri,That's a great looking site Sorcha linked. It look very thorough and the Real Audios should be a great help.
Just one small tip, from a friend who plays a lot to school groups and gets a lot of kids playing didge: at the stage of training the cheek muscles for circular breathing, it helps if you can immobilise the didge ... so you have both hands free ... and gently push in the sides of your cheeks, as you expel the trapped air.
I think this just helps focus your mind on the muscular action needed - and, once you get the idea, you can dispense with the prompt. One other though would be that you should not start out too optimistically ... don't try to get a really big didge resonating first off. I started with a couple of lengths of old 'Hoover' vacuum cleaner pipe. (Come to think of it ... there was a bit of a minor scandal some years back when a Northern territory Didgeridu competition was won by a bloke with a length of water pipe!)
BTW: My friend of the first suggestion reckons the best thing to start with is a length of 38mm (er ... 1½ inches in Noah's Ark units) PVC pipe. Smaller pipe seems to work well with littlies.
PS to BTW: On a site telling about cheap ways to make instruments, someone said K-Mart sold ready-made didges for 98¢ ... they were golf club handle protectors - plastic tubes wide enough to slip over a club handle, with a rolled over end that was small enough not to pass the handle ... making a great mouth piece.
Unfortunately, Australian K-Marts had never heard of them ... and the club protectors in golf pro shops were the new improved model ... with perforated sides to save weight and minimise condensation in wet weather ... and no good for didging!
Regards,
Bob Bolton