In the process of trying to work with MSCRM webservices via CodeIgniter, I ran across some articles asking about using nusoap in CI. I went ahead and rewrote the parts of the nusoap library so it will work with CI.
Just unzip this file into your libraries folder.
Call it using the standard library loader
Note: This requires that you've downloaded the standard nusoap files located here: http://sourceforge.net/projects/nusoap/ And have installed them relative to this file (in your library folder)
A working example: http://codeigniter.com/forums/viewthread/60879/