The G.E.C.K. (also known as the Garden of Eden Creation Kit) for Falout New Vegas is based on the Fallout 3 editor of the same name. It was released along with the U.S. version of the game on October 19, 2010. Like its counterpart, the G.E.C.K. is an application separate from the base game that is available for free download, and allows its users to create and modify content within their game. As it is dependant upon the game's main resources, it is necessary to have a copy of the base game installed in order for the G.E.C.K. to function.
With the G.E.C.K., users can create and edit any type of data, from quests to dialogue, landscape and character creation as well as scripting, resource and asset implementation. The capabilities of the G.E.C.K. may also be expanded further if used in conjunction with the Fallout New Vegas Script Extender(NVSE). This application not only extends the editor's scripting capabilities, but also allows for the creation of plugins, which add new features, functions, and content that would not otherwise be possible to implement. These plugins not only extend the base game, but may also add additional functionality to the G.E.C.K. itself, such as the ability to edit master files (.ESM).
The most recent version of the G.E.C.K., 188.8.131.528, was released in July of 2011, and is available for download via the official site.
Additionally, as of May 20th, 2013, it can also be downloaded from Steam.
A collection of tutorials, FAQs, and other valuable information may be found on the official G.E.C.K. wiki