On the topic of free stuff on Steam, Unreal Tournament 3 is available for free on Steam right now. This goes through the rest of the weekend.
I was incredibly confused, myself, when suddenly, Unreal Tournament 3 showed up on my games list. I thought maybe it was a free demo, like Valve did for L4D a few weeks ago (you could play the full game of L4D over the weekend for free, but it went away after the weekend).
But, by what I can tell at the moment, this is actually an offer to PERMANENTLY obtain the ENTIRE GAME, good for this entire weekend. Let me know if I'm wrong, because I really think I must be.
http://www.co-optimus.com/article/1876/Unreal_Tournament_Black_Free_on_Steam_this_Weekend.html
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