You need to register to get access to those games but it is worth it....
Note: Limited Period Offer. Each game have unique time limit to grab it.
Current Status: Open.
Free Game List:
World War III: Black Gold (Real-Time Strategy)
Earth 2150: Escape from the Blue Planet (Real-Time Strategy)
Robo Rumble (Real-Time Strategy)
The Troma Project (Turn-Based Strategy)
Commander – Conquest Of The Americas (Real-Time Strategy)
Septerra Core (Role-playing)
More Info: http://www.dlh.net/en/news/53526/free-strategy-games-steam-keys-this-weekend.html
Visit the above DLH Registration page link.
Login/Create a new account. Check for confirmation email and complete registration. Note[Tested]: You need to make sure that you don't use any temp email addresses. However, some like Moakt temp emails are accepted. Once you enter correct email address and unique nickname, the "Register" button is enabled. If not, refresh and try again with correct details.
Once logged in to the account, Click on "Nickname" or "Account name" -> Select "Steam Keys"
You'll locate all 7 steam games.
Under each game, Click "Like" and then Click "Get your Steam Game here".
Complete Captcha/trick to get the Steam Key. Note: In some cases, there may be delay in getting the Steam Key. However, please wait until you get it.
Activate the key ASAP.