I have a couple of Guest Passes for Red Orchestra which I picked up this AM during a random shopping spree :). The Guest Pass gives full access to the game for 10 days. First come, First serve.
I also have a gift copy of Half Life 2 that I never realized I had, again first come, first serve:
I guess we could use this thread as a catch all for these STEAM freebies.
Edit: Please PM the individual you would like the product from.