My list of httpd servers at
http://union.ncsa.uiuc.edu/HyperNews/get/www/httpd.html
references a review at http://mistral.enst.fr/~pioch/httpd/. It
references another one by Paul Hoffman.
Daniel LaLiberte (liberte@ncsa.uiuc.edu)
National Center for Supercomputing Applications
http://union.ncsa.uiuc.edu/~liberte/