Get your hands on already prepared raw Team Fortress 2 level and show your skills by creating the environment! More information about contest can be found here. Good luck!
A lot of concept art from Singularity by Raven Software. All stuff can be found here.
Check latest UDK Tutorials – How to Create a Playable Level in 11 Days posted on World of Level Design. You can read it here.
Robert Briscoe released few screens of his level remake called Dear Esther. More info and a video can be found here.
Short piece of information about creation process on level Tram from Natural Selection 2. Check it here.
Tristram Tunnels is an UDK scene made by Polycount member Darkrusader. Scene is based on original Diablo III concept art. More information can be found here.
Bioshock 2 Modular Environment Assets – link.
Results of Gameplay and Flow Challenge, contest from World of Level Design can be found here.
Short text about creation process of Battlefield: Bad Company 2 is available on CGSociety.
Article can be found here.