Heads up any fans in Australia who still don't own the show on DVD. JB Hi-Fi is selling the complete collection right now for $85, as opposed to the former retail price of $147.
They've also got Seasons 1-4 for $16 each and a box set of the movies for $30.
I just bought it today, and I am so happy! This is the cheapest I've seen it anywhere.
It doesn't come in a cool bender head like it does in the USA, but it does come in a box, containing individual DVD cases for each season and each movie - which is probably a lot more practical anyway.
You probably won't find it much cheaper.