Counter-Strike: Source Level Creation
http://developer.valvesoftware.com/wiki/Counter-Strike:_Source_Level_Creation

Dark Messiah Level Creation
http://developer.valvesoftware.com/wiki/Dark_Messiah_Level_Creation

Day of Defeat: Source Level Creation
http://developer.valvesoftware.com/wiki/Day_of_Defeat:_Source_Level_Creation

Half-Life 2 Level Creation
http://developer.valvesoftware.com/wiki/Half-Life_2_Level_Creation

Left 4 Dead Level Creation
http://developer.valvesoftware.com/wiki/Left_4_Dead_Level_Creation

Portal Level Creation
http://developer.valvesoftware.com/wiki/Portal_Level_Creation

Source Mods Level Creation
http://developer.valvesoftware.com/wiki/Source_Mods_Level_Creation

Team Fortress 2 Level Creation
http://developer.valvesoftware.com/wiki/Team_Fortress_2_Level_Creation

The Ship Level Creation
http://developer.valvesoftware.com/wiki/The_Ship_Level_Creation