Path of Exile

This game is free to play, and is still in beta! It's basically like diablo 3 should have been, except with a twist! You get your abilities through socketing gems to armor/weaponry and they level up over time making your abilities stronger! It's a really cool concept, and there are ways to make the orbs interact and give you more powerful and effective abilities!

http://www.pathofexile.com/

Amazing game, I've played it abit (lvl 27). It's really cool and fun, I would say it is more like Diablo 2 than Diablo 3 though.