It looks like at some point today you'll be able to download some retro titles from the Lucasarts back-catalog via the Steam download service.

Their Twitter account will tell you when they're actually available.
Here are the games they're releasing:

• Armed and Dangerous
• Indiana Jones and the Fate of Atlantis
• Indiana Jones and the Last Crusade: The Graphic Adventure
• LEGO Indiana Jones: The Original Adventure
• LOOM
  
• Star Wars Battlefront II
• Star Wars Republic Commando
• Star Wars Starfighter
• The Dig
• Thrillville: Off the Rails

A good mix of classics and modern classics available for download.