What tools make it easy to maintain (or avoid!) the N versions of your CV?
In addition to using LaTeX with a makefile, I find that using the LaTeX package splitbib is very useful. It allows you to format your publications with different subtitles for different category of publications, and you can pick and choose which entries from your publications (which I maintain as a BiBTeX file) should be included. 

Since LaTeX allows you to include files, it's relatively easy to create separate files that contain the base material and then include them as needed in different formats.