Radiant - Home of the GtkRadiant

Q3Map2 Handbook Beta Edition - Documentation of the great q3map2

Q3map2 Shader Manual - New shader manual by Obsidian and ydnar

q3map2 toolz - Very useful compiler frontend

Tram Design - Great forum!

2Bit - Wolfenstein Enemy Territory scripting and level design tutorials

ET Scripting Reference - Scripting commands of Wolfenstein Enemy Territory explained in detail

Splashdamage - The cool guys who created Wolfenstein ET and ET Quake Wars!

Splashdamage Mod Wiki - ET and ETQW mod documentation

modwiki.-net - Doom 3 and other id-Tech 4 engine games mod documentation

worldofleveldesign.com - Level design news & forum

katsbits.com - Great Blender tutorials & forum