This really depends on what you consider 'dying for the Doctor'.
If you try to count everyone who's ever died in the midst of his adventures—as the Doctor does when he's beating himself up with guilt—there are far too many to count. That's the whole point of Lorna Bucket's death scene in "A Good Man Goes to War".
If you only count people who intentionally sacrificed themselves to prevent him from doing so, the number is much smaller—River song in "Forest of the Dead", the Master in "The End of Time", and a few other characters in non-TV stories.
If you mean something in between, such as people who've died risking their lives to help him save the world, like Katarina in "The Daleks' Master Plan" or Adric in "Earthshock", the answer is… well, somewhere in between.