So I was told last night about a website which is dedicated to people who have multiple copies of some games or are feeling generous called Steam Gifts. This is an official website and sometimes even Valve officially put up their own give-away's on this site.
Steam Gifts is basically a bidding site with "points" instead of money, currently $212,000 worth of free games are being given out on this website, they even have some very nice people giving away DOTA 2 Beta, Skyrim and even MW3. How it works is simple..
DOTA 2 is estimated on steam to be worth $50 (new game price in the US)
$50 = 50 points
Therefore you can use 50 of your points to be entered into the draw. However once those points are used you WON'T get them back if you do not win the give-away, but you will get them back if you decide to un-enter BEFORE the competition is over.
Winners are decided randomly by a bot on the website
Point system is explained below and in the linkhttp://www.steamgifts.com/forum/lalkl/points-or-no-points
New members are all awarded 25 points when they create their account, but they must go through an authorisation process, which checks your Steam account and see how many games you have (to make sure your not just someone with 0 games on your steam looking for free-bees). Points are awarded on a weekly basis, these are just free points everyone who has an account gets. You also get points for doing your own give-away, say you bought a pack of games like The Orange Box but you already had Half-Life 2 well you could give that away on Steam Gifts for points towards getting another new games you might want for FREE!
There's only one DOTA 2 Giveaway I've found (15/11/11) which has only a week left so I cant enter for it because I'm a new member: link below http://www.steamgifts.com/giveaway/DLNbp/dota-2
So get yourself signed up and check back on the site as much as you can to find more DOTA 2 giveaways or what ever game you might want to get for FREE!!!
Thanks for reading and enjoy!