I did indeed.
The Adventures of Buckaroo Banzai: Across the 8th Dimension had Peter Weller, Ellen Barkin, John Lithgow, Christopher Lloyd, Rosalind Cash, Clancy Brown, Vincent Schaivelli, and…Yakov Smirnov! Jamie Lee Curtis’ scene was cut from the theatrical release.
The Faculty:
Elijah Wood
Josh Hartnett
Usher Raymond
Jon Stewart
You beat me to it. I still mourn the fact that Buckaroo Banzai VS The World Crime League was never made.
The Big Chill had these future stars:
William Hurt
Jeff Goldblum
Glenn Close
Tom Berenger
Kevin Kline
Mary Kay Place
JoBeth Williams
Meg Tilly
Kevin Costner’s corpse (It was his finest performance!)
Christopher Walken, Jeff Goldblum, Sigourney Weaver all appeared in “Annie Hall”.
and John Cusack!
Alien had Sigourney Weaver, Ian Holm, John Hurt, Yaphet Kotto, Veronica Cartwright, Harry Dean Stanton, and Tom Skerritt, which must be a record. Aliens wasn’t too bad either with Bill Paxton, Paul Reiser and Lance Henriksen.
The Deer Hunter (1978) had De Niro (granted, after Taxi Driver and Godfather Part II), Christopher Walken, and Meryl Streep.
**Apocalypse Now **had Martin Sheen, Larry Fishburne, Harrison Ford (post-Star Wars), and Dennis Hopper.
Platoon had future stars:
Willem Dafoe
Charlie Sheen
Forest Whitaker
John C. McGinley
Kevin Dillon
Johnny Depp
Dale Dye
And for bonus points, Carl Lumbly, Dan Hedaya, and Clancy Brown. Yow.
Also, how about John Boorman’s Excalibur? Liam Neeson, Gabriel Byrne, Patrick Stewart, Helen Mirren – and also the debut of twentysomething Ciaran Hinds, who’ll never be a household name but in the last several years you’ve seen him as the Russian president in Sum of All Fears, the singing theatre owner in Phantom of the Opera, the team leader in Munich, the sneering bad guy in Lara Croft, the snitch in Veronica Guerin, and who’s now set to play King Herod in the next big Bible epic – right after the Miami Vice flick comes out.
A bit off the subject, as this isn’t a movie, but does anyone remember the TV show “Buffalo Bill”? It starred Dabney Coleman, who was an established star at that time and also had John Fiedler (Mr. Peterson from the “Bob Newhart Show”). In addition to those two familiar actors, the cast included up-and-comers Geena Davis, Joanna Cassidy, Meschach Taylor, Max Wright (Willie Tanner from “Alf”), and Charles Robinson (Mac from “Night Court”). One of the few TV shows which you can watch today and recognize nearly everyone in it.
And is best known to Austen fans as Capt. Frederick Wentworth in Persuasion.
Me too. 
In the category of Movie with the most future stars, the winner is…
I don’t know, I can’t tell right now. I would have to sit down and analyze each list (Ex: in the Outsiders, Lieff Garrett would have to be out because he was already famous, Sofia Coppala never was a movie star, but she did win an Oscar, so she can get counted). Maybe a 7 way tie between Outsiders, Fast Times at Ridgemont High, Dazed and Confused, American Graffitti, School Daze, Can’t Hardly Wait, Big Chill, and Adventures of Buckaroo Bonzi. Dang, I got to make a lot of statues.
By my count, it’s School Daze. With the exceptions of Ossie Davis, Sam Jackson, Joe Seneca and former child star Lawrence Fishburne, nobody else in School Daze had much prior movie experience or TV exposure. Even Spike Lee had only shot the super-guerilla She’s Gotta Have It and his student films at that point.
Even if you leave Spike, School Daze still has a solid 11 actors who got career starts and went on to other projects.
More from School Daze:
Giancarlo Esposito, Erik Dellums (both recurring characters on Homicide: Life on the Street)
Singles is a treasure trove of breakout stars, though most of them weren’t actors:
Bridget Fonda
Kyra Sedgwick
Bill Pullman
Cameron Scott
Pearl Jam
Alice in Chains
Soundgarden
If this thread were about individual directors instead of individual movies, Cameron Crowe and Spike Lee would be running neck and neck. Alan Parker would be a close third.
Oh, let’s not forget Earth Girls are Easy:
Geena Davis
Julie Brown
Jeff Goldblum
Jim Carrey
Damon Wayans
No landmark of great cinema, this is best thought of as a student film with a very serendipitous cast.
[nitpick] Campbell Scott. [/nitpick]
Buckaroo Banzai was 1984. Back in 1975, Lloyd and Schiavelli appeared with Danny DeVito, Brad Dourif, Anjelica Huston, and Louise Fletcher in One Flew Over The Cuckoo’s Nest.
The 1957 film Hell Drivers, besides starring the incomparable Stanley Baker, included in its cast a pre-Bond Sean Connery, pre-Prisoner Patrick McGoohan, pre-Doctor Who William Hartnell, pre-Carry On Sid James, David McCallum near the start of his career, and a whole pile of familiar British actors (Robin Bailey, Alfie Bass, John Horsley, Gordon Jackson, Herbert Lom, George Murcell, Wensley Pithey)* … one heck of a cast list, in my opinion!
*Well, I know who all those people are …
***THE MOVIE WITH THE MOST STARS/FUTURE STARS EVER… HAS GOT TO BE …
STAR TREK… THEY INCLUDE:
WALLACE SHAWN. JAMES WORTHY
MICK FLEETWOOD. ANDREA MARTIN
STEPHEN HAWKING. SETH MACFARLANE
DWAYNE JOHNSON. IGGY POP
BRIAN SINGER. CHRISTIAN SLATER
KELSEY GRAMMER. KEN JENKINS
King ABDULLAH bin AL-HUSSEIN. KIRSTEN DUNST
KIRSTIE ALLEY. JASON ALEXANDER
CHRISTOPHER LLOYD. ASHLEY JUDD
TERRI HATCHER. TOM MORELLO
SARAH SILVERMAN. KIM CATTRALL
KURTWOOD SMITH. JAMES CROMWELL
NIKKI COXX ***