The screenshots, video files, artwork and various other bits and pieces have been collected from a number of sites across the world. These sites deserve credit for this:
Fragile Mortality (marked with 'fm')
GameSpot (marked with the GameSpot 'G')
Gamepost (marked)
Computer Games Online (CDMAG)
PC Gamer (US) (marked)
Shuga Shack
Half-Life.de
http://www.creativelevels.de/