Demystify the Source SDK with this handy guide.
The purpose of this page is to answer most of the commonly asked questions about Scripting and problems related to Scripting.
Basically a gathering together of ideas on how to make a map scary to the player.
This is basically a document that highlights all of the important changes from HL1 to HL2 mapping.
A tutorial on how to change the format of the menu. Be advised that this is not a tutorial one how to create graphics or art, but simply how to alter the menu format for your mod.
Here's the list of other command-line parameters.
Commons errors when working with Source
How to use Pakrat
Player Size Information. (Danial at Chatbear did some tests and put this together)
A mini tutorial on how to record in game action to produce a movie that will run in most media programmes.
How to Install Maps
Make a simple mini mod without coding
VERC: Half-Life 2 and Source Mod FAQ