COMMAND & CONQUER: RED ALERT
Westwood’s alternate history spin-off is still a great RTS, and one of a number of classics in the genre available for free. Visit CNCNet and you’ll find downloads of Command & Conquer, Red Alert and Tiberian Sun, all updated to work nicely on modern systems and integrated with the CnCNet multiplayer platform for easy online play. If that isn’t enough to sate your RTS desires, the brilliant Twisted Insurrection — available from the same site — is a total conversion of Tiberian Sun, available standalone. And, for fans of Westwood’s main competitor, Battle.net lets you download StarCraft for free.