Yes, I know it's kind of late, but a lot of you might not of saw this around steam. So I will post it here.

If you have steam (if you don't just make one for free) and you have ATI or nVidia you will get certain games free. I list them below.

ATI Card Users:

Half-Life2: Deathmatch + LostCoast, More information here.

nVidia Users:

Portal: First Slice, more information here. EDIT: It also includes HL2 DM and Lost Coast.

Also, a page here is giving you 50% off (scroll down on page) of three steam games for all steam users.