Picked up PS2 Wipeout Fusion and GC Beyond Good and Evil for $AUS15 each complete at a pawn shop, and in return for driving my dad across town, he bought me PS2 Ace Combat Squadron Leader for $AUS30 second hand at a gamestore as well.. pretty decent considering I've only ever seen it either $AUS100 new or $AUS80 second hand at EB.
Also, if you're anywhere near Harvey Norman in Midland, Western Australia in the next few months (and I'm sure most of you are), keep an eye on their price for PS2 GT4 - it's already 50% off, and they had about 8000000000 copies of it.