For "third party mods", I'd like to garner some attention for two high-quality mods for Command and Conquer: Generals - Zero Hour by the same team.
-
Shockwave is a (much) more of the same take on the game: among other features, it features three new generals, myriads of units and new commander powers.
-
Rise of the Reds features a new faction (yes, you guessed well, Russia), along with numerous improvements for the old ones.
While (to the best of my knowledge) they can't be played in campaign mode, they do support a seriously improved AI for skirmish battles which can and will keep you on your toes.