Try the PIONEER website.  They have a lot of musicals which are inexpensive in the royalty market (compared to Tams-Witmark, etc.), but are hilarious for the audiences.  Ones that have been extremely well received at our high school:  Tied to the Tracks, Wagon Wheels West, The Lady Pirates of Captain Bree, Give My Regards to Broadway, The Ransom of Red Chief, Orphans in Candyland.

Others that we can't do because of strict standards, but I would love to do:  Ducktails and Bobbysocks; Flapper; Oh, Horrors! It's Murder!; A Connecticut Yankee; Lucky Dollar, Private Eye

Other scripts I have my eye on that I will do eventually:  The Secret Garden (PIONEER--not the Broadway version), A Little Princess; Sleepy Hollow

In response to the dispute about the Copyright Term Extension Act, I don't agree that it's a good thing.  For all of the works which were set to soon enter the public domain when it was passed, it fails to promote progress  (the Constitutional intent of copyrighting in the first place) because they have already been created.  All it does for those works is continue to limit their exposure and dissemination.  Even theoretically legally-protected fair uses (such as parody) are often curtailed through legal action if the copyright owner is powerful enough.  While a creator is alive, protecting his interest is fine, but once he's dead, other policy considerations (like allowing free exchange of ideas) should carry the day.