The initial version of the Source SDK has been released.
You need to own a Source game to have access to the SDK.
This release includes Source tools and work-in-progress
documentation. These tools allow creation of Counter-Strike Source
maps, models, and materials. Once the SDK is downloaded and
installed, all tools, example content and documentation will located
in your Steam folder Steam\SteamApps\<account>\sourcesdk. Tools like
Hammer and Half-Life Model Viewer can be started directly from the
Steam SDK menu.
The Source SDK will be continously updated, this first
release doesn't contain any source code to build customized server &
client binaries (Mods).
For help on the SDK release visit http://collective.valve-erc.com/