These tools of mine operate outside of the game, and do not actually require the game to be present at all. Most of this stuff is intended for quite experienced NWN custom content / module authors - that is, technically experienced, I can use these just fine and I don't have much idea about module construction plot-wise...

NeverBlender NeverBlender
"The One True Modeling Tool At It Again"
NeverBleder: You've never seen more wretched hive of swearing and forced whitespace. Hopefully this will make using Blender to model stuff for Neverwinter Nights some day a possibility.
nwscript-mode for Emacs nwscript-mode for Emacs
"The One True Editor At It Again"
nwscript-mode is an editing mode for Emacs (and XEmacs), for those who want to edit with the One True Editor and compile with Torlack's compiler, rather than relying on the slow, Unholy, Most Clumsy toolkit.
PW Character Archiver PW Character Archiver
"Those who forget history are doomed to repeat it"
PW Character Archiver is a tool for maintaining a decent character history with PWs. It can also be used to easily maintain zillions of versions of your character files... A good tool for those who prefer to save things. Blah blah. Go use it already. =)
Data tools Data tools
"How to lie with statistics"
Data tools are extremely ugly Perl scripts to convert data to XML and allow you to lie with statistics. Some Perl and *NIX guruhood required to operate. Includes a hideous hack to turn your character archive into a useless graph.

Also, sshotcollect, for which I have not yet made a fancy button.