William Hartnell played the First Doctor from 1963-1966, and again for the story "The Three Doctors"(1972-1973).
Jon Pertwee played the Third Doctor from 1969-1974(while his first episode aired in January 1970, the first block was mainly recorded in 1969). He returned for "The Five Doctors"(1983), Dimensions in Time(1993) and the two BBC Radio stories The Paradise of Death(1993) and The Ghosts of N Space(recorded in 1994, aired in 1996).
Tom Baker played the Fourth Doctor from 1974-1981. He returned for Dimensions in Time(1993). Since 2009 he has been playing the Fourth Doctor in audio adventures. He also reprised the role for "The Day of the Doctor"(2013).
Peter Davison played the Fifth Doctor from 1981-1984(again his first episode only aired in 1982, but was recorded some time earlier the previous year). He returned for Dimensions in Time(1993). He has been playing the Fifth Doctor in Audio Adventures since 1999. He also reprised the role for "Time Crash"(2007).
Colin Baker played the Sixth Doctor from 1984-1986. He returned for Dimensions in Time(1993). He has been playing the Sixth Doctor in audio adventures since 1999.
Sylvester Mccoy played the Seventh Doctor from 1987-1989. He made appearances as the Seventh Doctor, such as Dimensions in Time(1993), and thus could be said to have been the "current" Doctor until his appearance in The TV Movie(1996). He has been playing the Seventh Doctor in audio adventures since 1999.
Paul Mcgann appeared as the Eighth Doctor in The TV Movie(1996). He read audiobooks for the BBC, such as Earth and Beyond(1998). Since 2000 he has been playing the Eighth Doctor in audio adventures(again the first story was released in early 2001, but recorded in 2000.) He also reprised the role in the Night of the Doctor(2013).
Christopher Eccleston played the Ninth Doctor in 2005(though episodes were recorded the previous year).
David Tennant played the Tenth Doctor from 2005-2010(his final episode was recorded in 2009). He also reprised the role for the Day of the Doctor(2013).
Matt Smith played the Eleventh Doctor from 2010-2013.