We have EBGames here in Australia as well. Latest Games only though. Gametraders is a pretty good company though. They are each independent franchises but link through a national database, and have games dating back to NES. So if the store doesn't have it, they find out if any other does and simply puts you in contact. It about US$10 for a PS1 game, US$23 for PS2, US$15 for N64 carts without cases (add $8 for a wrinkly old box), and US$20 for Dreamcast games. Reasonable but by no means a bulk buyers bargain.
Video games heaven was another, but they seem to have moved out of my local shopping centre. They had all Atari Carts for US$4.
I guess as I appear to be the only Australian here, this information is useless though.
But internationally, how about cash converters. They always have a huge stock of games.