Musicals 101
Musicals 101: How Broadway Musicals Are Made
It is a very comprehensive site on the Broadway musical. Though most of the site deals with Broadway, this particular page is very informative on how musicals are made. It is applicable for on OR off-broadway.
Musicals 101
Musicals101: Homepage
This site from Musicals 101 provides a very comprehensive site dealing with all aspects of musicals. Includes great material for schools wanting to put on a musical. Over 330 biographies plus lots of history.