This week, entries into Valve's Content Description Record database for Steam have leaked the games that will be available to Linux users, at least during the beta phase.
Those games are Amnesia: The Dark Descent, Crusader Kings 2, Cubemen, Dynamite Jack, Eversion, Galcon Fusion, Serious Sam 3: BFE, Solar 2, SpaceChem, Steel Storm: Burning Retribution, Superbrothers: Sword and Sworcery EP, Trine 2, Waveform and World of Goo.