NIF is a popular file format used by 3D games such as Morrowind, Oblivion, Civilization IV, and many more. The Blender NIF scripts enable you to read and write files that are compatible with these games in Blender.
This release fixes some bugs related to Fallout 3 export (in particular those with multiple objects using the same textures), and features improved (but still experimental) import and export for Sid Meier's Railroads.
You can grab the latest version of the scripts here:
https://sourceforge.net/project/showfiles.php?group_id=149157&package_id=166219
For more documentation and help with the scripts, visit the wiki or the forum:
http://niftools.sourceforge.net/wiki/Blender
http://niftools.sourceforge.net/forum