No famous relations, but here is an expanded list from a previous similar thread in 2003:
When I was a child:
Captain Kangaroo
David McCallum (Ilya Kuryakin on “The Man from U.N.C.L.E.”).
For 12 years I worked in the IMAX theater at the National Air and Space Museum. This gave me lots of opportunities to meet celebrities.
Aviation/Space:
Chuck Yeager (a conceited jerk, he spoke at NASM every year on the anniversary of his breaking the sound barrier)
Jeana Yeager (no relation) and Dick Rutan, who flew around the world non-stop, unrefueled in Voyager.
Scott Crossfield, first man to fly twice the speed of sound.
Patty Wagstaff, aerobatic champion
Kathryn Sullivan, Shuttle astronaut
Jim Lovell, Apollo 13 astronaut
Judy Resnik, Shuttle astronaut (died in Challenger)
Authors:
Milbourne Christopher, magician, Houdini biographer
Isaac Asimov (book signing)
Milton Glaser, graphic designer
James Randi
Mark Okrand, creator of the Klingon language
Murray Gell-Mann, physicist
Phil Plait (Bad Astronomer)
Christopher Hitchens
Kurt Vonnegut
Carl Sagan and wife Ann Druyan
Philip Morrison, nuclear physicist
Eugene Wigner, nuclear physicist
Richard Rhodes (The Making of the Atomic Bomb)
Thor Heyerdahl
Leonard Maltin
Garrison Keillor (book signing)
John Allan Paulos (Innumeracy)
Dava Sobel (Galileo’s Daughter, Longtitude)
Al Gore (weeks before being nominated for VP. I gave him a little tour of the museum after he gave a a talk about his book. Nice guy, and not nearly as stiff as he later seemed.)
Racecar drivers:
Mario Andretti
Al Unser, Jr.
Bobby Rahal
Roberto Moreno
Gregg Moore
Parker Johnstone
Jan Beekhuis
Chris Economaki, sportcaster
Entertainment:
Steve Goodman, musician
Alex Trebek (when I was on Jeopardy! – really!)
Pete Seeger (to my dismay, I annoyed him by taking too many pictures during a rehearsal)
Penn and Teller (book signing)
James Doohan (Scotty on Star Trek
Ron Silver, actor
Jerry Mathers (Leave it to Beaver)
Kristin Chenoweth, Tony-winning Broadway performer
Larry King (I gave him a tour of the museum)
John Denver (was standing in line for tickets to the IMAX theater)
Walter Cronkite (I was walking across the lobby, and he was standing there all by himself. I introduced myself and asked if he was meeting a museum representative. He said no, and asked if I’d show him the Enola Gay exhibit, which I did. Very nice man.)
The directors of virtually every IMAX film ever made (including To Fly! and Everest–same guy), but you probably wouldn’t recognize their names.
David Breashears, 5-time Everest summitter
Jack Nicholson
John Travolta
Mythbusters Adam Savage, Jamie Hyneman, and Kari Byron
Steve Oedekerk, writer, director (Ace Ventura, Patch Adams)
Brett Leonard, director (Lawnmower Man, Virtuosity)
Ang Lee (director of Life of Pi, Brokeback Mountain)
Douglas Trumbull (special effects wizard: 2001, A Space Odyssey, Blade Runner)
Ben Burtt, Oscar-winning sound designer (Star Wars, Indiana Jones, etc.)
Frank Marshall, producer (Indiana Jones, E.T., etc.)
Roy Disney
Don Hahn, producer (Beauty and the Beast, The Lion King)
James Cameron
Harrison Ford (I was present at the recording session for a film he narrated)