To celebrate the upcoming release of Command & Conquer 4, EA has released Tiberian Sun and it’s expansion, Firestorm as freeware.
Tiberian Sun was the sequel to the original Command & Conquer and Renegade. This is the third game in the series to be released as freeware, the other two being the original Command & Conquer and Red Alert. You can download it at the link below, the file size is 1.2 GB.
Since they appear to be going in order of release, my guess is that the next game they release, if they choose to, will be Red Alert 2.