Unreal Engine - Free
Today Epic Games have announced that their Unreal Engine is now free for all uses, with a 5% royalty.
Unreal Paris - Virtual Tour
Explore a beautiful Parisian apartment running in real-time on the Unreal Engine 4.
Dynamic Lighting Gameplay with UE4 and Enlighten using Blueprints
Geomerics have posted a detailed article on how they used Unreal Engine together with Enlighten.