I haven't tried to do a full profile of each cast member; just a few random facts and selected filmographies (some more selective than others -- I'm a bit inconsistent) for each main actor. :)
Nathan Fillion (Mal)
Gina Torres (Zoe)
Alan Tudyk (Wash)
Adam Baldwin (Jayne)
Jewel Staite (Kaylee)
Sean Maher (Simon)
Summer Glau (River)
Morena Baccarin (Inara)
Ron Glass (Shepherd Book)
Chiwetel Ejiofor (The Operative)
David Krumholtz (Mr. Universe)
Nathan FillionBirth: March 27, 1971 in Edmonton, Alberta, Canada
Random Facts: Fillion, who actually auditioned for the role of Angel when Buffy the Vampire Slayer was being cast, originally wanted to be a high school English teacher, but (obviously) became an actor instead. He was nominated for a Daytime Emmy Award in 1996 for his role as Joey Buchanan on One Life to Life, but lost to Kevin Mambo from Guiding Light.
Selected Filmography: One Life to Life, 1994-1997; Saving Private Ryan, 1998; Two Guys, a Girl and a Pizza Place, 1998-2001; Buffy the Vampire Slayer, recurring 2003; Miss Match, recurring 2003; Slither, 2006; Lost, 1 episode 2006; White Noise 2: The Light, 2007; Waitress, 2007; Drive, 2007
On the Web: @ IMDb
Gina TorresBirth: April 25, 1969 in New York City, New York, USA
Random Facts: The youngest of three children in a Cuban-American family, Gina Torres is not only an actress but also a gifted singer who majored in voice at an arts high school in New York. She married actor Laurence Fishburne in 2002.
Selected Filmography: M.A.N.T.I.S., 1994; Hercules: The Legendary Journeys, recurring 1997-1999; Cleopatra 2525, 2000-2001; Alias, recurring 2001, 2005, 2006; Angel, recurring 2003; The Matrix Reloaded and The Matrix Revolutions, 2003; Hair Show, 2004; 24, recurring 2004; The Shield, recurring 2006; Standoff, 2006-?; I Think I Love My Wife, 2007
On the Web: @ IMDb, Gina-Torres.com
Alan TudykBirth: March 16, 1971 in El Paso, Texas, USA
Random Facts: When Serenity was released, Alan Tudyk was starring on Broadway in Monty Python's Spamalot in the classic roles originated by John Cleese in Monty Python and the Holy Grail -- Lancelot, The French Taunter, Knight of Ni, and Tim the Enchanter. Before Serenity, he was probably one of the best-known Serenity castmembers to the general public, having played the highly memorable role of Steve the Pirate in Dodgeball: A True Underdog Story. Upon hearing of Firefly's cancellation, he threw a "We don't work for Fox anymore" party for his cast and crewmates; ironically, he later appeared on fellow Dodgeball actor Jason Bateman's TV show Arrested Development, meaning that, for one episode at least, Tudyk did in fact work for Fox once again. Arrested Development was later cancelled by the network.
Selected Filmography: 28 Days, 2000; Wonder Boys, 2000; Strangers With Candy, 2 episodes 2000; A Knight's Tale, 2001; Hearts in Atlantis, 2001; Ice Age, 2002; Dodgeball: A True Underdog Story, 2004; I, Robot, 2004; Rx, 2005; Arrested Development, 1 episode 2005; Into the West, 2005; Ice Age 2: The Meltdown, 2006; Death at a Funeral, 2007; Knocked Up, 2007; 3:10 to Yuma, 2007
On the Web: @ IMDb, AlanTudyk.com
Adam BaldwinBirth: February 27, 1962 in Chicago, Illinois, USA
Random Facts: Baldwin, who once worked as a truck driver, is married with three children. He is not related to the other Baldwins (you can tell cause he's taller and better looking than they are) but he has worked with at least two of them in the past.
Selected Filmography: My Bodyguard, 1980; Ordinary People, 1980; D.C. Cab, 1983; Hadley's Rebellion, 1984; Reckless, 1984; Bad Guys, 1986; 3:15, 1986; Full Metal Jacket, 1987; Next of Kin, 1989; Radio Flyer, 1992; Eight Hundred Leagues Down the Amazon, 1993; Blind Justice, 1994; Independence Day, 1996; The Cape, 1996-1997; The Visitor, recurring 1997-1998; Dr. Jekyll & Mr. Hyde, 1999; The Patriot, 2000; The X-Files, recurring 2001-2002; The Keyman, 2002; Gacy, 2003; Angel, recurring 2004; The Inside, 2005; The Poseidon Adventure (TV), 2005; Day Break, 2006-2007; Sands of Oblivion (TV), 2007
On the Web: @ IMDb, Adam Baldwin Archives
Jewel StaiteBirth: June 2, 1982 in White Rock, British Columbia, Canada
Random Facts: Jewel has been acting since a very young age, and appeared in The X-Files episode Oubliette when she was 14. In 1998, she was nominated for a Gemini award (like the Canadian version of the Emmys) for Best Performance in a Children's or Youth Program or Series for the series Flash Forward. She and Nathan Fillion, by the way, are the only two Canadian actors to play leads on any of Joss Whedon's shows. :)
Selected Filmography: Flash Forward, 1996; Space Cases, 1996; Da Vinci's Inquest, 1998-2000; Higher Ground, 2000; Just Deal, recurring 2002; Wonderfalls, recurring 2004; Window on the Hill, 2005; Stargate: Atlantis, recurring 2005-2007
On the Web: @ IMDb, Jewel-Staite.net
Sean MaherBirth: April 16, 1975 in Pleasantville, New York, USA
Random Facts: Maher has a Bachelor of Fine Arts in Drama from New York University. He's been a regular castmember on not one, not two, but three Fox shows that were cancelled in their first season. Man, that must be frustrating. He was apparently prone to calling Summer Glau Summer instead of River during filming on Firefly.
Selected Filmography: Ryan Caulfield: Year One, 1999; The $treet, 2000; Party of Five, recurring 2000; Brian's Song, 2001; The Dive from Clausen's Pier, 2005; Living 'til the End, 2005; Wedding Wars (TV), 2006
On the Web: @ IMDb, Shiny
Summer GlauBirth: July 24, 1981 in San Antonio, Texas, USA
Random Facts: Glau trained as a ballerina throughout her childhood, and was home-schooled by her mother for several years in order to accommodate her ballet schedule. As a teenager, she sustained a serious injury which forced her to take some time off from ballet. It was after this that she decided to pursue a career in acting. Fittingly, her first major acting role was the prima ballerina in the Angel episode "Waiting in the Wings."
Selected Filmography: Angel, 1 episde 2002; Cold Case, 1 episode 2003; CSI, 1 episode 2004; Sleepover, 2004; The 4400, recurring 2005-2007; Mammoth (TV), 2006; The Initiation of Sarah (TV), 2006; The Unit, recurring 2006-2007
On the Web: @ IMDb, SummerGlau.co.uk
Morena BaccarinBirth: 1979 in Rio de Janeiro, Brazil
Random Facts: Born in Brazil but raised in New York City, Baccarin is the daughter of a Brazilian actress named Vera Setta. She attended the Juilliard School in New York, and had almost no professional acting experience when she was cast in the role of Inara on Firefly. She actually joined the cast late, replacing Rebecca Gayheart, who left the show after one day of shooting.
Selected Filmography: Perfume, 2001; Way Off Broadway, 2001; Roger Dodger, 2002; The O.C., 3 episodes 2006; How I Met Your Mother, 1 episode 2006; Stargate SG-1, recurring 2006-2007; Sands of Oblivion (TV), 2007; Heartland, 2007
On the Web: @ IMDb, Morena Baccarin Online
Ron GlassBirth: July 10, 1945 in Evansville, Indiana, USA
Random Facts: Ron Glass started his career on the stage, making the move to television in 1972 with a guest spot on Sanford and Son. In 1982, he was nominated for an Emmy Award for his work on Barney Miller. He is currently Chairman of the Board at the Al Wooten Jr. Heritage Center, a youth center dedicated to providing opportunities, academic help, and positive examples for children in Los Angeles.
Selected Filmography: Barney Miller, 1975-1982; Gus Brown and Midnight Brewster, 1985; Perry Mason: The Case of the Shooting Star, 1986; Deep Space, 1987; Amen, recurring 1989-1991; Rugrats, 1992-2004; Mr. Rhodes, 1996-1997; Teen Angel, 1997-1998; Shark, 2 episodes 2006
On the Web: @ IMDb
Chiwetel EjioforBirth: July 10, 1974 in London, England
Random Facts: Ejiofor is British-born of Nigerian background. For his role in the play Blue/Orange, he won the award for Most Promising Newcomer at the 2000 London Critics Circle Theatre Awards (Drama). He was nominated for several awards for his role in the 2002 film Dirty Pretty Things, and again found himself receiving much acclaim for his work in 2005's Kinky Boots.
Selected Filmography: Amistad, 1997; G:MT Greenwich Mean Time, 1999; It Was An Accident, 2000; My Friend Soweto, 2001; Dirty Pretty Things, 2002; Trust, 2003; Twelfth Night, or What You Will, 2003; 3 Blind Mice, 2003; Love Actually, 2003; Red Dust, 2004; Four Brothers, 2005; Slow Burn, 2005; Kinky Boots, 2005; Inside Man, 2006; Children of Men, 2006; Tsunami: The Aftermath (TV), 2006; Talk to Me, 2007
On the Web: @ IMDb
David KrumholtzBirth: May 15, 1978 in New York, New York, USA
Random Facts: Krumholtz was originally cast in the role that eventually went to David Strickland on the Brooke Shields sitcom Suddenly Susan. He can now be seen playing Charlie every week on CBS's show Numb3rs.
Selected Filmography: Life With Mikey, 1993; Addams Family Values, 1993; The Santa Clause, 1994; Monty, 1994; Chicago Sons, 1997; The Ice Storm, 1997; Slums of Beverly Hills, 1998; The Closer, 1998; 10 Things I Hate About You, 1999; Liberty Heights, 1999; How to Kill Your Neighbor's Dog, 2000; The Trouble With Normal, 2000-2001; The Mexican, 2001; Sidewalks of New York, 2001; According to Spencer, 2001; Big Shot: Confessions of a Campus Bookie, 2002; You Stupid Man, 2002; The Santa Clause 2, 2002; Scorched, 2003; Kill the Poor, 2003; The Lyon's Den, 2003-2004; Looking for Kitty, 2004; Harold and Kumar Go to White Castle, 2004; Ray, 2004; Numb3rs, 2005- ; Max and Grace, 2005; American Storage, 2006; Bobby, 2006; The Nail, 2006; Live!, 2007
On the Web: @ IMDb, Slobbering David Krumholtz Groupies