Be ready to be flooded by new ripped up urban landscapes, plasma weapons and wasteland wanderers. Bethesda Softworks has released the editor for Fallout 3.

Called the G.E.C.K. after the famed device from the game, the program arms the community with tools that will allow players to expand the game any way they wish. Users can create, modify, and edit any data for use with Fallout 3, from building landscapes, towns, and locations to writing dialogue, creating characters, weapons, creatures, and more.

And the download is only 9M.

http://fallout.bethsoft.com:80/eng/downloads/geck.html