This list came from the website http://www.dunemessiah.com/
WARNING! Some spoilers below the list of novels!
Dune - 1965
Dune Messiah - 1969
Children of Dune - 1976
God Emperor of Dune - 1981
Heretics of Dune - 1984
Chapterhouse: Dune - 1985 (Chapterhouse: Dune is the final book in this epic story)
Dune: House Atreides (1999) and Dune: House Harkonnen (2000) were ritten by Brian Herbert and Kevin J. Anderson. They are prequels to the original novel, and it looks like there are going to be more.
Paul M’uadib is pretty much non-existant by the 3rd novel; the main characters in “Children of Dune” are (surprise!) his two sons. “God Emperor of Dune” takes place 1000 years after CoD; the onlycharacters from the earlier books are Leto II (Paul’s son) and a revived Duncan Idaho. Leto II bites it in GEoD, leaving Duncan as the last “man” standing for the last two novels.