Try:

Local:

http://www.dvdcrave.com.au
(generally cheap prices)

http://www.game.com.au
(can't really think of any other cheap aussie sites for games)

Overseas (I think the PS3 is region-free, but don't quote me on that, just google it and try these sites):

http://www.play-asia.com
(hong kong based. US and Asian games. always reliable, weekly specials)

http://www.gameplay.co.uk/
(UK based. great source for PAL versions of games that is usually out there before our shores)

http://www.videogamesplus.ca/
(Canadian site. Our dollar is pretty strong against the CND so this is a great place to import US games)


These are all sites I've used and enjoyed.