Here’s an updated list of TCM tributes.
(Nov. 1, 2014: Adds John Cleese on W.C. Fields, Jamie Leigh Curtis on Janet Leigh, Naked and Famous rock video of Joan Crawford; adds writer/editor and production company credits for Guillotine Post)
(Nov. 2, 2014: Adds Dennis Hopper on Nicholas Ray)
(Dec. 3, 2014: Adds Woody Allen on Ingmar Bergman — not online)
Please let me know if I have missed one.

Prince Albert of Monaco on Grace Kelly
Woody Allen on Ingmar Bergman (not online)

Anonymous on June Allyson
Anonymous on Mary Astor
Anonymous on Robert Benchley
Anonymous on Audie Murphy
Anonymous on Kim Novak

Claire Bloom on Charlie Chaplin
Ann Blyth on Joan Crawford
Ernest Borgnine on Robert Ryan
Carol Burnett on Lucille Ball

Michael Caine on Cary Grant
Keith Carradine on Greer Garson
Harry Carey Jr. on John Wayne
Richard Chamberlain on Claude Rains
Cher on Katharine Hepburn (low quality)
Patricia Clarkson on Ingrid Bergman
John Cleese on W.C. Fields (added)
Guillotine Post: Written by James Curtis; TCM producer Jeanne Franz; editor Michael Koepenick

Jamie Leigh Curtis on Janet Leigh (added)
Tony Curtis on Cary Grant

Doris Day on Doris Day
Doris Day on Rock Hudson
Laura Dern on Barbara Stanwyck
Michael Douglas on Kirk Douglas (not online)

Clint Eastwood on James Garner

Michael Feinstein on Fred Astaire
Carrie Fisher on Debbie Reynolds
Guillotine Post: TCM writer/producer Ruth Anna Millman; editor Michael Koepenick

Peter and Jane Fonda on Henry Fonda
John Frankenheimer on Burt Lancaster

Sir John Gielgud on Claude Rains (not online)
Kelsey Grammer on Lauren Bacall
Lee Grant on Ida Lupino
Melanie Griffith on Jean Harlow
Guillotine Post: TCM writer/producer Ruth Anna Millman; editor Michael Koepenick

Molly Haskell on King Vidor
Monika Henreid on Paul Henreid 
Sir Anthony Hopkins on Katharine Hepburn
Dennis Hopper on Nicholas Ray
Anjelica Huston on Walter and John Huston

Bill Irwin on Harold Lloyd

Maria Cooper Janis on Gary Cooper
Shirley Jones on Burt Lancaster

Janet Leigh on Norma Shearer (not online)
Jennifer Jason Leigh on Barbara Stanwyck
Jack Lemmon on Billy Wilder
Richard Lewis on Buster Keaton
Nigel Lythgoe on Ginger Rogers

Rob Marshall on Sophia Loren
Liza Minnelli on Vincente Minnelli
Julianne Moore on Myrna Loy

Naked and Famous Joan Crawford rock video.
Paul Newman on Elizabeth Taylor

Mary Ann Owen on Donna Reed

Chazz Palminteri on Edward G. Robinson
Gregory Peck on Lauren Bacall

Brett Ratner on Kirk Douglas (video pauses)
Robert Redford on Natalie Wood
Guillotine Post: Writer/producer Ruth Anna Millman; senior editor Michael Koepenick

Burt Reynolds on Spencer Tracy
Kurt Russell on Elvis Presley
Guillotine Post: TCM writer/producer Jean Franz; editor Michael Koepenick

George C. Scott on James Cagney
Nancy Sinatra on Frank Sinatra
Kevin Spacey on Jack Lemmon
Meryl Streep on Bette Davis

Elizabeth Taylor on Montgomery Clift
Marlo Thomas on Loretta Young (may not play)

John Waters on Vincent Price
Oprah Winfrey on Sidney Poitier