Any good, free games for a low end pc?

I got into pc gaming a few weeks ago after i built my pc and it has been a blast, the only thing i dont like is that i dont have very many games and the few i want to play, i dont got the specs the run them at the moment. I will list my specs down below and say any free games that you guys think i should try out(i have already tries tf2, tribes, world of tanks and planetside 2 already)

 

AMD 16-5400K 3.6 GHz

AMD RADEON 7540d HD graphics w/ 1gb of vram

3 gigs on on board memory at 1866 mhz

1366x768 32" tv as a monitor :(

 

I really like it i just need some more games to play until i can get a bit more money.

I like source games and i can play on all high and get 60 fps, so any of those besides black mesa which ive already played will be nice, thanks and have a nice day!

Racing games from Codemasters like DiRT series will work fine on this hardware. Not free though.

There's War Thunder, Tribes: Ascend and League of Legends, but well, they each target specific audience. Not sure you'll like them.

i already play league and tribes and they are fun every once in a while, anything else?

Warframe

Alien Swarm

Team Fortress 2

World of Tanks

Nothing here requires an earth shattering system. Hopefully this helps

i said i already played 2 of those and im not really interested in alien swarm...

Here's a neat list by PCGamer. I personally like the listed adventure games.
http://www.pcgamer.com/2013/09/21/the-50-best-free-pc-games/ 

warframe, arctic combat, red eclipse

Well damn