SmallTownGuy
My son got me playing Spiral Knights. It has Mac, Linux, and Win versions, it's pretty fun, and I think I'll do ok as a free-to-play player. But they don't have the sense of community that zOMG has. And they do a lot to encourage players to buy chance items and perks.
I've played this with friends too. A definitely worthwhile suggestion. I think the download itself is only 100mb or the likes, so very economical and light on your computer. It's also decently fun. Maps tend to get a bit repetitive but it has a real charm of its own.
4laugh