Sean Maher was born on April 16, 1975 in Pleasantville, NY.
He trained at NYU and acted on stage in several productions. After graduating in 1997, he got the lead role in 1999 on Fox's "Ryan Caulfield:Year One" about an 18-year old police rookie. The show was cancellled after two episodes.
He next had a recurring role in 2000 on Party of Five's last season as Adam Matthews, Julia's final love interest.
Staying with Fox, he was cast in "The $treet" as Mark McConnell. McConnell was a Navy SEAL from a blue-collar background who was now living the high life of a Wall Street trader.
From there, he starred in Disney's remake of "Brian's Song" in which he played Brian Piccolo.
Then, lucky us!, he was cast as Simon Tam in Firefly!
There is mention made of his having composed the music in 1998 for a movie "Guru in Seven", but as that is only mentioned on one site, I'm not sure of the accuracy of it.
Sean Maher Filmography (IMDB)
Shiny - Sean Maher Fan Listing