In addition to the HL2 DM update, there are also other updates ready to be drooled over. For starters, the code for making HL2/Source mods is now ready and this also includes mapping, modeling and other things. Character samples and examples of a mod are included with exporters for 3D Studio Max and Maya.

Below is the full list of information, courtesy Jess Cliffe, Valve Software:

Half-Life 2/Source SDK

• Includes game code needed to create Half-Life 2/Source MODs
• New Half-Life 2 sample character model
• Ability to edit Half-Life 2 maps
• Maya model exporter
• 3d Studio Max model exporter source code
• Sample MOD with vehicles
  

Source Updates

• HTTP and non-HTTP map auto downloading functionality
• Enhanced dedicated server logging capabilities
• Various tweaks and fixes