I’m a Believer- The Monkees
As I Lay Me Down to Sleep - Sally B. Hawkins
Somewhere Out There - Linda Rondstadt & James Ingram
Get off My Cloud - Rolling Stones
You Ain’t Seen Nothin’ Yet - Bachman Turner Overdrive
Be - Neil Diamond
Summer Nights - Olivia & Travolta
“I’m So Bad (Baby I Don’t Care)” by Motorhead
I’m Looking Over a Four Leaf Clover
Oh What a Beautiful Morning
You Are My Sunshine
Mine is Feel Inside (and stuff like that). Actual song is about 10 minutes into the video, but the rest of the video is a big part of what makes it so feel-good. 
Yes! “Shambala” and “Walking on Sunshine” were what came to mind immediately when I saw the thread title.
"Happy Trails" Roy Rogers & Dale Evans
also-
“She’d Rather Be With Me” The Turtles
“Wooly Bully” Sam The Sham And The Pharoahs
“She Loves You” Fabs
“Daydream” by The Lovin’ Spoonful.
“Hold Your Head Up” by Argent is a great feel-good song, at least for anyone who has enjoyed the best episode of the short-lived but excellent cable series Men of a Certain Age.
I Don’t Feel Like Dancing - Scissor Sisters
I Get Around - Beach Boys
Home - Edward Sharpe and the Magnetic Zeros
I just thought of another:
I Just Want to Celebrate by Rare Earth
Fantastic, thanks.
I love this thread. So many many many great songs.
I’m too young to have experienced big band music first hand (really!) but my parents listened to it and it still makes me smile and feel happy. My mom especially loved The Andrews Sisters:
“Boogie Woogie Bugle Boy of Company B”
“Bei Mir Bist Du Shein”
“Run and Coca Cola”
“In the Mood” - Glenn Miller Orchestra, Or really, any music you can swing dance (this is a medley of various songs) or Lindy Hop to, or anything at all by Cab Calloway , especially while marveling at the Nicholas Brothers
Or hell, just “Sing Sing Sing” (Benny Goodman, with Gene Krupa on drums)
Rockabilly and dancing to it is fun too.
This song isn’t very well-known and neither are the singers, but The Boswell Sisters were huge influences on The Andrews Sisters and those that came after. Anyone who can listen to this without a huge smile on their face is probably dead and should see a doctor immediately.
“(We’ve got to) Put That Sun Back In The Sky” - The Boswell Sisters
The song “Sweet Georgia Brown” is well-known but the singer Rose Murphy isn’t, though she did have a fun song, “Pennies From Heaven,” in the movie The Artist. Her versions are always delightfully demented (that’s her playing piano too).
A modern group tipping their hats to that old music is Leftover Cuties. I particularly love “Smile Big”
For good measure, how about some silly lollipop and popsicle songs:
“Lollipop”_The Chordettes
“My Boy Lollipop” - Millie Small
“Popsicles and Icicles” - The Murmaids
Clouds - Zach Sobiech
The link is a cover by some celebrity folk who got wind of his plight (high school student stricken with cancer who recently passed away).
The cover by Bad Manners makes me feel good, too. The goofy 80s “everybody dance around and mug for the camera” video doesn’t hurt.
Cecilia and Don’t Bring Me Down are a couple more fun stompy ones in the vein of My Sharona.
Is it too pretentious to request that the moderator change the thread name to “The Ultimate Feel-Good Song Thread?”
Just askin’.
https://www.youtube.com/watch?v=XQmBXEZEYtg “Sunshine, Lollipops and Rainbows” – Lesley Gore
Two artists previously mentioned, but with different, even more feel-good songs.
Jimmy Cliff: Wonderful World, Beautiful People
Shonen Knife: It’s A New Find
I can’t believe we’ve gone this far and no Jimmy Buffett!
"It’s Five O’Clock Somewhere with Alan Jackson
“One Particular Harbor”
ETA: How could I forget Why Don’t We Get Drunk and Screw"?
Since we’re talking Buffett, how about Love and Luck?