Blizzard has made three classic games available on Battle.net: Diablo, Warcraft: Orcs and Humans, and Warcraft 2: Tides of Darkness.
Diablo, released in 1997, features 16 levels of dungeon delving and allows multiplayer with up to three other players.
Warcraft: Orcs and Humans, released in 1994, is a real-time strategy game with 21 bonus maps and two-player versus mode.