Dawn of the Tiberium Age (DTA) is a stand-alone mod that combines Tiberian Dawn (C&C 95) and Red Alert. While classic mode gets as close to the original game-play and balance as possible, Enhanced mode provides improved game balance and a lot of fun new stuff. DTA features many customization options for Skirmish and multiplayer (where you can play as GDI, Nod, Allies and Soviet on over 200 maps), challenging original singleplayer missions, as well as co-op missions. Since this is a stand-alone mod, you don't require anything but the mod itself to be able to play: the original game is not required.
The latest DTA update (version 1.1476, released today) includes LAN multiplayer support. The LAN lobby works like the one in Tiberian Sun, automatically detecting other players and games on the same network. No internet connection is required or used.
Well, this is potentially slightly to moderately interesting.