NCCS has a variety of tools available to help with classification:
NCCS and IRS NTEE-CC vs. Foundation Center NTEE-XP Coding Systems
There have been two versions of NTEE since the mid/late 1990s when the IRS adopted NTEE for classifying new organizations. Due to IRS IT limitations, they required a simplified system so NCCS worked with them to implement the “NTEE-CC” (“core codes”) system and adopted it ourselves. This reduced the number of codes and eliminated the separate “common code” field. The Foundation Center maintained the original version of the NTEE system and has continued to expand the number of categories.
We expect that we will be working to recombine our systems in 2012 but in the meantime, there will continue to be significant differences in coding systems. Which is “better” really depends on what you need it for.