Don’t Know Much – Aaron Neville and Linda Ronstadt
Missing You – John Waite and Alison Krauss
Rich Woman – Robert Plant and Alison Krauss
Almost anything by the B-52s
This Is Us – Emmylou Harris and Mark Knopfler
I Wanna Sing that Rock and Roll – Gillian Welch and Dave Rawlins
Proud Mary – Ike & Tina Turner
Crying – Roy Orbison with kd Lang
Just out of Reach – Patsy Cline and Willie Nelson (so what if their tracks were recorded 30 years apart?)
Does Peter Paul and Mary count? If so, a bunch of their stuff
Roberta Flack and Donnie Hathaway did a number of very nice duets
Stevie Nicks/Kenny Loggins - Whenever I Call You Friend (well, I don’t think it’s cheesy)
“That Lovin’ You Feelin’ Again” by Roy Orbison and Emmylou Harris.
The Jesus and Mary Chain w/Hope Sandoval-“Sometimes Always”
Snow Patrol and Martha Wainwright, Set the Fire to the Third Bar.
But really, it’s not a duet. One hell of a support/backup singer, yes. But there’s no dialog in the song.
Interesting to see how many people have listed country songs, as most of what I’d have thought of would be in that genre.
There’s a brilliant cover of Don’t Give Up by Willie Nelson and Sinead O’Connor.
Also, Nanci Griffith’s Gulf Coast Highway, and covered by Emmylou Harris and Willie Nelson.
Iggy Pop and Debbie Harry take on Cole Porter together in Well Did You Evah. Sauced again.
Isobel Campbell of Belle & Sebastian, has since they broke up released 3 solo albums: Ballad of the Broken Seas,, Sunday at Devil Dirt and Hawk. All are duets with Mark Lanegan formerly of Screaming Trees and Queens of the Stone Age. Here they do Come Undone.
Very cool.Now that’s a duet.
Allmusic says:
It’s tempting to say something facile like “beauty meets the beast” in writing about this collaboration between former Belle & Sebastian member Isobel Campbell and Mark Lanegan, best known for his work with Screaming Trees and Queens of the Stone Age. After all, Campbell’s voice is all sweet angelic whisper while Lanegan’s whisky-and-nicotine rasp sounds like the product of ten thousand nights in a barroom, but somehow these sweet and sour elements come together with striking and impressive results on Ballad of the Broken Seas.
Damn, now I got nuthin 
Steve Earle “I Remember You”
I’m pretty sure that’s Emmylou Harris singing with Mr. Earle.
Another one: Stevie Nicks/Don Henley - Leather and Lace
Carly Simon & James Taylor Mockingbird.
I fucking love that song.
It is. She’s done loads of great duets, many more than mentioned here already. The two albums with Gram Parsons are among the greatest music ever made.
Not sure if it’s ever been recorded, but I twice got to see Jimmy Buffett and Maria Muldaur sing “Let’s Get Drunk and Screw”…
(This was back in the PPH days…)
Tramp - Otis Redding and Carla Thomas
Nathaniel Merryweathers “Lovage” Music to make love to your old lady by is a fantastic album pretty much all the way through and is mostly duets
I don’t know if this counts as pop or rock, but “Who”, by David Byrne and St. Vincent, is pretty good.
“All The Roadrunning” - the entire album by Mark Knopfler & Emmylou Harris