What are some good bands that use harmony a lot?

Chili Peppers! Especially a lot of vocal harmonies.

a newish band called fleet foxes have excellent harmony.

Lennon and McCartney are arguably the best ever.

And the Beach Boys were excellent harmonizers, as were the Byrds, the Turtles, Buffalo Springfield, and Crosby, Stills and Nash, but I think I may be dating myself here.

Just a tad, whatthefluther ;)
Although you forgot Simon & Garfunkel. And the Eagles have their harmonizing moments too.

I’ve always liked King’s X for their harmonies.

The Eagles

I agree with gooch – the eagles

Queen had a great harmony. The Beatles’ harmony on “Because” (from ‘Abbey Road’) is a great example of how good their voices worked together.

trivium frequently has some pretty sweet harmonized guitar solos, but I guess, technically, that would make it a duo?

CSN&Y

I confess, I don’t know what those bands sound like so I’m not sure if this is a good suggestion or not but I recently got turned on to The Raveonettes. My all time favorite for harmony though is the Indigo Girls!

Boston?

bad religion

XTC

grateful dead