I just saw on the Steam forums that you can create an account on Telltale's site to get a code for a free copy of episode 1 of their new Back to the Future adventure game in February:
http://forums.steampowered.com/forums/showthr … d.php?t=1711343 (Direct link: http://www.telltalegames.com/bttfoffer )

I signed up and got a code. They asked for my email and mailing address, but not credit card number or anything like that. They did send a confirmation email without warning that included my account name and password, which was kind of annoying.