The .nif importer/exporter for blender was designed for version 2.36.... and says there may be a bug due to changes in the animation system in Blender 2.37
Regardless, it is a matter of double-clicking on a different exe, because Blender hosts all versions.
Anyways, the readme seems to talk about how to export UV maps, (skins), animations, and models.
And Blender, you can have ......tonight.... I can't find the link to the exporter, however. Someone else posted it, its on sourceforge:
http://niftools.sourceforge.net/
Note, it does not support export for Maya yet.
So save your pennies... and go open source!!! Do not be afraid.
Be safe and get 2.36, or be current and get 2.37a, or be uber, and get 2.40 alpha2
http://www.Blender.org
I am trying it as we speak, and it requires the armature (bones) to be converted to a mesh object... which is possible, of course, just need to find how.