Good Strategy/RTS games?

Stacraft II. This game is considered pricey, but for me, I think it's all worth it. It's the only game I play because I haven't found any other more interesting ones. You can develop your skills and the Starcraft community is generally very nice :) And, it's satisfying to kill someone of higher rank than you, knowing that you melted their army, which took them 15 minutes to make :)