Since none of the diffs sites are carrying the into on the UI changes between 2.4.2 and 3.0.1 i generated some diff files for the entire interface earlier
you can view them here:
WotLK Interface Diffs
New files to note: Movieframe files in FrameXML, the VehicleUI under Addons, and the RuneFrame files in FrameXML
EDIT: link now has directory indexes (proper ones, if the icons don't work get a decent browser)
Updated to v2.3.2 against v3.0.1 build 8820, Alpha diffs moved to Here
New new files to note: more prtected execution stuff added, CraftUI removed, presumably consolidated into TradeSkillUI, SparkleFrame (aah Mista Sparkle :P) for goodness knows what, take a wander :-)