The Beatles “You Won’t See”
John and George are singing “la la la” in the background while Paul is singing.
Simple Minds
“Don’t You Forget About Me”
The Ramones did have la-la-la in “Howling at the Moon”.
Others :
Jon Secada - “La,la,la”
Who’s Afraid of the Big Bad Wolf? (tra-la-la-la-la)
Kermit the Frog - The Rainbow Connection (not mentioned yet?)
Randy Newman - I Love LA
Nitpick – The “Hey Jude” lyrics are na na na
You Won’t See Me.
That’s what I meant. 
The greatest song EVER!!!
My vote goes for Johnny B. Goode as recorded by the Sex Pistols.
Kyle Quit the Band by Tenacious D.
"Last week, Kyle quit the band.
Now we’re back together.
Misunderstanding, didn’t understand (doesn’t matter)
Now we’re back together again.
**La la la la la **. [sub][nice enunciation, too][/sub]
Couldn’t split up Kato and Nash (that’s true)
Couldn’t split Tango and Cash (that’s also true)
This is our song of exaltant joy, because …
We only came to kick some ass.
Rock the fucking house, and kick some ass."
also
Any song sung by the Phoebe Buffay (Lisa Kudrow) on Friends
“Jersey Girl,” by Tom Waits.
There’s a good live version featuring Tom Waits and Bruce Springsteen that’s been floating around for a while on Napster-esque file-sharers.
The Beatles’ “I’ve Just Seen A Face”
I think Deanna Carter sings “We Danced Anyway.” The line is about not knowing the words to a song, so they sang “la la la la la la la.”
La la love you, by Pixies.
Goodbye Earl by the Dixie Chicks.
My Cherie Amore
on the more obscure side, “My Favorite Song” by Lifestyle has a lot of la la la la la’s in it. It also will rock your arse. it’s on their new ep Frontier.
“Working Undercover for the Man” off the new They Might Be Giants album has sha la la la in it.
Gimme back my points. That’s the first song I thought of when I saw the subject. Just to be different, I’ll recommend Liz Phair’s cover version.
Or you could go with La Bamba by Richie Valens. Los Lobos also did a good cover and Weird Al Yankovic did a parody called Lasagna.
And wasn’t there some cheesy seventies power ballad called Thunder Island?
Another Zep Song: Goin to California
Barenaked Ladies, Blame it on Me.
La-La Means I Love You … The Delfonics
One with plenty of "la"s but perhaps a too child-like bent is “Kiss the Girl” from Disney’s “The Little Mermaid”. Plus the chorus actually does start with a “sha”, so it’s not a pure “lalala”. But it’s still so good!