To commemorate the Steam client's arrival on the Mac today (Valve is so going to dominate the Mac gaming world), everyone can now download Portal for free! The game's demo is attached to the Steam profile by default but now it is full product that is being offered. If you are one of those unfortunate people who have yet to play this demented little first person "shooter", here's your chance to get the game. The offer doesn't last forever though, only until the 24th of this month. If you don't have a Steam account, it's free to create one and it will not cost you anything to use it. Download this game immediately!