Just thought I'd put together a small list of useful resources covering UnrealScript for those of us who have no idea where to start learning.
The Unreal Source
Use WOTGreal Exporter (http://www.wotgreal.com/wotgreal/files/wotgrealExporter.zip) to view and extract the .uc class files.
There is a selection of useful examples contained within. Also useful is the complete UT source collection: http://www.gamefront.com/files/9652545/UT_v436_ScriptSource. Be advised this is the UT source, though, not DX.
The UnrealScript Language Reference
Which is located here: http://unreal.epicgames.com/UnrealScript.htm
It's not a tutorial per se, but contains some useful info.
The Unreal Wiki UnrealScript Tutorials
All pretty much unfinished and neglected, but still definitely worth the read. Located here: http://wiki.beyondunreal.com/Legacy:UnrealScript and http://wiki.beyondunreal.com/Legacy:UnrealScript_Lessons
These videos
http://dl.deathtouchstudios.com/videotutorials/UnrealScriptSeries/
And the associated forum thread over @ epic games: http://forums.epicgames.com/showthread.php?t=708162
I realise most of you will find this laughable, but for those of us who would like to learn to code for Unreal-based games, especially those of us who want to start even now in 2011 (like me!), it's invaluable as there actually isn't a lot out there in terms of documentation.
~Shin.