Ah, Duets!
Well... Off the top of my head...
"The Tennis Song", "What You Don't Know About Women", "You're Nothing Without Me" - City of Angels
"A Man", "Worth It" (which is not published, but worth searching out) - Weird Romance....
Jose, the two
Weird Romance songs have been published in the songbook, but it's now out of print. I have it. I looked on Amazon.com and someone is trying to sell it for
$73.79!!

And two of my favorite duets: "Beauty That Drives a Man Mad" from
Sugar (although I do prefer, and have actually performed, the version that was used in the London production of
Some Like It Hot...we had it transcribed from the recording

) and "We Are Women" from
Candide.
There are also the Singer's Musical Theatre Anthology Duets books.