UDK is the actual Engine behind Unreal.
Website:
http://www.unrealengine.com/udk/
UDK Games
http://en.wikipedia.org/wiki/List_of_Unreal_Engine_games
Tutorials
http://www.worldofleveldesign.com/categories/cat_udk.php
https://www.3dmotive.com/library_guest
http://udn.epicgames.com/Three/WebHome.html
http://willyg302.wordpress.com/2011/10/
http://www.design3.com/training-center/engines-sdks/udk/coding/introduction-to-c-programming-via-unrealscript
http://udn.epicgames.com/Three/VideoTutorials.html#3D Buzz Video Tutorials - Using UDK
http://www.unrealengine.com/en/udk/documentation/
http://labs.vectorform.com/2011/11/creating-a-side-scrolling-game-with-udk/
http://udn.epicgames.com/Three/UnrealScriptReference.html
http://www.magicstonestudios.com/
Forum
http://forums.epicgames.com/forums/366-UDK
Assets
http://udkresources.com/
Objectives
Add models, run animations
GUI
Game Manager scripts