I Am Legend: 1954 novel, adapted to film three times - The Last Man On Earth (1964, with Vincent Price) The Omega Man (1971, with Charlton Heston) and the 2007 film of the same title starring Will Smith.
Hell House: 1971 novel, source for the 1973 film The Legend of Hell House.
The Night Stalker, a Made for TV Movie adaptation of a (then unpublished) novel by Jeffrey Grant Rice, and its sequel TV movie, The Night Strangler. Both movies were huge ratings hits, which led to the development of the series Kolchak the Night Stalker (which Matheson was not involved with).
The short stories "Prey" and "Nightmare at 20,000 Feet" ("There's...something on the wing!"). "Prey" was adapted into one of the stories in the TV movie Trilogy of Terror, "Nightmare" into a Twilight Zone episode. Both adaptations have been critically acclaimed.
The short story "Button, Button," which was also adapted into a Twilight Zone episode and then the movie The Box.
Duel, a short story that was made into the first film directed by Steven Spielberg.
"The Splendid Source", a 1956 short story adapted into an episode of Family Guy in 2010.