This is the Nethack bestiary.  The accompanying perl script
nhtohtml.pl takes a local nethack source distribution and parses
several monster-related files to produce the results.  

The html subdirectory contains the full bestiary.  The index can be
found in html/index.html

No warranty, etc.   Contributions are welcome.  I've only tested on
Mozilla Firefox, so your mileage on MS IE will vary.