I am looking for the formal name of a song commonly referred to as
Puccini's Love Song. The only information I know is that the version I
am looking for is song as a duet with a female singer. I believe Donna
Summer also did a version of the song I am looking for.

Just a shot in the dark:  could Donna Summer's song have been "Love to
Love you Baby", maybe a version of "O Mio Babbino Caro. Lilting
melodic love song from the one-act Italian opera by Giacomo Puccini",
"Gianni Schicchi" ??

The Italian title means "o my dear baby", hence my guess.

Puccini's operas contain many love songs.
In his time, opera composers almost intended that such songs would
become popular and "hit the street", as they did.

Where do we start:  Tosca, La Bohème, Manon Lescaut, ...?
http://www.r-ds.com/opera/pucciniana/operas.htm

There are collections of his "greatest love songs":
http://cd.ciao.co.uk/Puccini_s_Greatest_Love_Songs_Pavarotti__6063470

It looks like there's an arrangement of a Puccini aria/duet that has
been done for brass band, and titled as "Puccini's Love Song." (The
title shows up in books of band arrangements.) Myoarin, or someone
else who has a more thorough knowledge of Puccini than I do, can
probably identify the actual song seconds into the clip on the page
below (track #8). I know I know it--but I can't put a name to it at
the moment.

http://www.bernaertsmusic.com/06PAGES/03CD/CDbb/CDBB17.htm

Two well-known pop songs based on Puccini arias are "Turning Back the
Hands of Time," by Neil Sedaka (based on "Nessun Dorma," from
"Turandot") and "Don't You Know," by Bobby Worth (based on "Musetta's
Waltz" from "La Bohème"). The latter was widely popularized by Della
Reese.

I haven't found any reference to Donna Summer doing any versions of
Puccini. She did, however, record Con Te Partiro (I Will Go with You;
also translated Time to Say Goodbye) in a dance version (!), which
appeared on the VH1 release "Live and More Encore." The song is by
Quarantotto, and is probably better known as recorded by Andrea
Bocelli(he also recorded it as a duet with Sarah Brightman). There is
a clip of Bocelli singing the song on Barnes and Noble.

http://music.barnesandnoble.com/search/product.asp?z=y&EAN=724355651129&ITM=2

Here's a clip of Summer's version on Amazon:

http://www.amazon.com/gp/product/B00000JBEA/ref=s9_asin_more/102-1935543-4537722?n=5174

Thank you thursdaylast23-ga! I located the song I was looking for. The
song is Time To Say Goodbye by Andrea Bocelli (not Pucinni). The link
you provided to Barnes & Noble for the Sarah Brightman CD Time To Say
Goodbye was EXACTLY what I was looking for. Thanks for you help.