Want to make your own professional quality video games for free? The Unreal Development Kit is a modding/engine crafting tool available for free download at http://www.udk.com/download. Professional games that use the Unreal engine include BioShock, Mass Effect, Gears of War, and Batman: Arkham Asylum. YouTube user TheNewBoston has been kind enough to upload tutorials detailing exactly how to use the software, and after a call to fellow developers, his site now offers over 800 tutorials from different people in and outside of the industry. Check it all out at www.thenewboston.com.
The New Boston Tutorial on Youtube.