There's one called 'The Crypt of Riddles' which you could dissect thoroughly. It has a nice variety of riddles and many scripts that would be useful when creating your own version.
http://nwvault.ign.com/Files/modules...59355261.shtml
Oh, and I see there's a follow-up as well
http://nwvault.ign.com/Files/modules...26286940.shtml