mines are:

boy meets girl
roxette
hall and oates
erasure
savage garden

My list would include:

Air Supply
Simon & Garfunkel
Sonny & Cher
Homer & Jethro
The Judds
The Carpenters
The Righteous Brothers
The Everly Brothers
Donny & Marie Osmond
Johnny & June Carter Cash

Carpenters
Air Supply
Hall & Oates
Savage Garden
Everly Bros.

Pet Shop Boys
Erasure
Simon And Garfunkel
Hall And Oates
Goldfrapp

I totally forgot to add Simon & Garfunkel. D'OH!!! I'd also add June & Johnny Cash, plus Ashord & Simpson and Marilyn McCoo & Billy Davis, Jr.

The Righteous Brothers
Don & Duey(they pretty much taught the Righteous Bros everything they know)
Hall & Oates
Marvin Gaye & Tammi Terrell
Nino Tempo & April Stevens
Billy Vera & Judy Clay
Mickey & Sylvia
The Everly Brothers
Sam & Dave
Bob & Earl
Sonny & Cher

^ Yes, Marvin & Tammi were a wonderful act, too. It's a shame things ended for them both so young, so tragically. May they both :rip:.

Dolly Parton & Kenny Rodgers - Islands in the stream
http://www.youtube.com/watch?v=lixDK_tMEhE

Mariah Carey & Trey Lorenz - I'll Be There
http://www.youtube.com/watch?v=52d20PK_Kyk

The Judds

Although no longer a duo, They Might Be Giants (John Linnell and John Flansburgh).