I went to Xavier High School, a prestigious Jesuit institution in New York. There’s a smattering of mayors and congressman (including a former mayor of New York), but by far the two biggest names on the list are Supreme Court Justice Antonin Scalia and NBC weatherman Al Roker. Curiously, they always lead with Roker in the promotional material.
Yours?
I went to a tiny high school in a tiny town in extreme remote northern Maine.
Me. I’m the most notable person from my high school. As far as I know.
We did this a month ago.
http://boards.straightdope.com/sdmb/showthread.php?t=498093&highlight=alumni+famous
Grant Hill, I think. I don’t know of any others who are particularly famous.
I graduated from Klein High School. As far as I know the only notable from there is http://www.imdb.com/name/nm0005164/bioLyle Lovett.
Although I’ve been a fan for years and have met members of his extended family, and I still live in the same area–I’ve never met or seen him IRL.
From Wikipedia:
The guy who invented spinners!?! The Violent Femmes! Who the hell is Speech?
I went to a weird high school…
Randy Arney (co-founder of the Steppenwolf Theater in Chicago,) Uwe Blab (basketball Player) and Brian Shouse (former Cardinals baseball player.) I think that’s it.
My high school has a Wikipedia page, which surprises me; it looks like a student wrote it, which does not. The following are listed as “notable alumni”:
* Khalif Barnes, offensive tackle, Jacksonville Jaguars
* Robert Griffith, Strong safety, Arizona Cardinals
* J Robinson, head wrestling coach for the Golden Gophers
* "Shotgun" Tom Kelly, local radio/TV personality; currently DJ in LA for KRTH (K-Earth 101FM)
* Hula, a talk show host on Channel 93.3
* Kalvin Reed, a talk show host on Channel 93.3
* Phillip Gaughen, Radio personality in San Diego for KGB 101.5
* Tom Gatch, Writer/Columnist, Author of "Hooked on Baja" (W.W. Norton & Co./ Countryman Press)
* Raymond Wells, middle linebacker, San Francisco 49ers, Tennessee Titans
I’ve only heard of Tom Kelly, who is strictly small potatoes.
Winona Ryder.
That’s it. My hometown is pretty dull.
Field Marshal Paulus (of Stalingrad fame)
I come from a very poor, tiny high school in Louisiana. My graduating class was 39 people and I was the only one that went straight to a 4 year college. I am afraid that I might be the most notable although certainly not the most famous. We had a large number of people that went on to commit serious felonies including horrible and senseless murders.
Prince Charles would probably top the list for my school although he only went there for a year. Of the people who graduated, probably Kerry Packer, media magnate.
I went to a Jesuit school: St Aloysius’ College, at Milsons Point in Sydney. I’d say the most famous old boys are Sir Charles Mackerras, the conductor and Tony Abbott and Joe Hockey, federal politicians.
Pared down from Wiki’s rather long list, to show the genuinely famous or near-famous, IMHO:
* Jerome "Jay" Apt, Class of 1967, astronaut
* Chris Frantz, Class of 1970, drummer for The Talking Heads
* Edgar J. Kaufmann, American department store magnate (Kaufmann's) and philanthropist. In 1935, Kaufmann commissioned famed American architect Frank Lloyd Wright to build his much-celebrated summer home, Fallingwater, in the Laurel Highlands outside of Pittsburgh.
* David McCullough, Class of 1951, two-time Pulitzer Prize-winning author and historian
* Tom Vilsack, Class of 1968, former governor of Iowa, Secretary of Agriculture for the Obama AdministrationDr. Walter S. Baird - physicist
Evan Farmer - actor / TV personality (Of 'While You Were Out" fame)
Harris Glenn Milstead - better known as the movie actor “Divine”
Michael Phelps - 14 time Olympic Gold Medalist and swimming world record holder
Double O Swango Valedictorian, graduated year ahead of me.
Russel Brand. 
Washington-Lee HS in Arlington VA
Forrest Tucker (actor), 1938
Gena Rowlands, 1947
Shirley MacLaine, 1952
Nancy Dussault, Actress and Broadway musicals singer and dancer, ABC’s Good Morning America co-anchor with David Hartman, 1953
Pat Priest, Actress The Munsters, 1954, [1]
Warren Beatty, 1955
George Lee Butler, Commander in Chief, USSC, 1957
Robert Richardson, Nobel Prize-winning physicist, 1955
Jake Scott, 1963 (two time Super Bowl champion w/ Miami Dolphins: Super Bowl VII and Super Bowl VIII| VIII]])
Stan Winston (film director, visual effects supervisor),1964
Dan Rizzie (artist),1969
Reggie Harrison, 1969 (two time Super Bowl champion w/ Pittsburgh Steelers: Super Bowls IX and X)
Carl Tanner, (World-class opera tenor), 1980
Sandra Bullock (actress), 1982
And MEEEEEEEE! 1962
Daryle Lamonica, NFL Raiders Quarterback
Johnny Estrada, All-star, pro-baseball player
Chad McCarty, pro-soccer player, Olympian
Mark Gardner, pro-baseball player
Stephen Spach, pro-football player
Keith Poole, pro-football player
Amber Frey - G/f of convicted murderer Scott Peterson
Adam Carolla was two years behind me at my high school.
Erin Moran (of “Happy Days”) was two years ahead of me.
Those are the two that I knew about before going to the Wikipedia site. Several others are listed there.
Ed