Now don't start thinking OMZG DIZ HAZ 2 B HAXORZ!!
This is just a very simple way to get some free VC that is totally legit. But it does require you to have played some other games on steam
Now remember all those cards you would get while playing steam games? Well they get thrown into your inventory and apparently people will buy that stuff from you (who knew right).
All you need to do is put it up for sale in the steam market and you can start earning some free money. This will be added to your steam wallet which you in turn can use to buy VC.
As they will be going for about 0.04 cents or something like that you won't be getting a lot. but if you have about 50 cards you could get around 2 bucks from that! which means 5000 free VC.
Here is the steam help page if you need help finding out how to do this http://steamcommunity.com/tradingcards/faq/