Captain & Tennille
I grew up on them so they hold a special place. But people may not realize how amazing they were production-wise. Listen to "Shop Around." Check out their website: http://www.captainand tennille.net
Carpenters
Another group I grew up on. Just can't beat the voice of Karen.
ABBA
The Swedish group that understood what Phil Spector was trying to do and made "The Wall of Sound" go one better!
Peter, Paul & Mary
Not a '70s group, but one of my all-time favorites -- I still see them in concert every year.
The Four Tops
My ultimate Motown group. "Standing in the Shadows of Love" and "Bernadette" are classics -- as is Levi Stubbs!