As for 3/4 Time Pieces:
Debussy - "La plus que lente" (the "slower than slow" waltz). Yes, it does lean towards the
salon side of Debussy's output, but it's a lovely piece, and I actually like it better when I hear it played a bit more "sentimentally" than some purists would prefer. I first heard Andre Watts play this on a Live From Lincoln Center recital. And I played it on my first full recital in college.
Chopin - The Waltzes, The Mazurkas.
"Hello, Young Lovers" from
The King & I. Pianist, Stephen Hough, has a lovely transcription of this song.
"The Carousel Waltz" from
Carousel - Such an amazing "prologue". -And Stephen Hough also performs a transcription of this one - amazingly virtuosic without sacrificing flash for substance.
"When I'm Not Near The Girl I Love" from
Finian's Rainbow.
"Come To Me, Bend To Me" from
Brigadoon.
"Lay Down Your Head" from
Violet.
"Where's My Shoe?" from
She Loves Me - albeit a very fast "waltz".

"Before I Gaze At You Again" from
CamelotFauré - "Après un rêve" - Both in the original vocal version, and the instrumental transcriptions.
Mozart - "Deh vieni non tardar" - Yes, technically it's in 6/8, but it's still very lilting.
Ned Rorem - "Early in the morning" - This has to be one of my all-time favorite American art songs. The poem and music perfectly convey the memory of having breakfast in a Parisian café - with a touch of bittersweetness. I think the term "painfully beautiful" applies to this two-page masterpiece.
Early In The Morning
Ned Rorem
Text: Robert Hillyer
Early in the morning
Of a lovely summer day,
As they lowered the bright awning
At the outdoor cafe,
I was breakfasting on croissants
And café au lait
Under greenery like scenery,
Rue François Premier.
They were hosing the hot pavement
With a dash of flashing spray
And a smell of summer showers
When the dust is drenched away
Under greenery like scenery,
Rue François Premier,
I was twenty and a lover
And in Paradise to stay,
Very early in the morning
Of a lovely summer day.