Agatha Christie: The Miss Marple Mysteries

Main Character: Miss Jane Marple, elderly spinster and amateur sleuth
Location: St. Mary Mead and other locales, mostly in England
Bold type indicates a book I've read.

1. Murder at the Vicarage (1930)
2. The Tuesday Club Murders (1932), aka: The Thirteen Problems
3. The Regatta Mystery (1939)
4. The Body in the Library (1942)
5. The Moving Finger (1943)
6. Mousetrap & Other Stories (1950)
7. A Murder is Announced (1950)  [See Review]
8. Murder with Mirrors (1952), aka: They Do It With Mirrors
9. A Pocket Full of Rye (1953)
10. What Mrs. McGillicuddy Saw (1957), aka: 4:50 from Paddington
11. The Adventure of the Christmas Pudding (1960)
12. Double Sin & Other Stories (1961)
13. The Mirror Crack'd (1962), aka: The Mirror Crack'd From Side to Side
14. A Caribbean Mystery (1964)
15. At Bertram's Hotel (1965)
16. Nemesis (1971)
17. Sleeping Murder (1976)

Agatha Christie: The Hercule Poirot Mysteries

Main Character: Hercule Poirot, Belgian private investigator
Setting: mostly England
Bold type indicates a book I've read.

The Mysterious Affair at Styles (1920)
Murder on the Links (1923)
Poirot Investigates (1924)
The Murder of Roger Ackroyd (1926)
The Big Four (1927)
The Mystery of the Blue Train (1928)
Peril at End House (1932)
Thirteen at Dinner (1933)
Murder on the Orient Express (1934), aka: Murder in the Calais Coach
Murder in Three Acts (1935)
Death in the Air (1935), aka: Death in the Clouds
The A.B.C. Murders (1935)
Murder in Mesopotamia (1936)
Cards on the Table (1936) Poirot / Ariadne Oliver  [see review]
Poirot Loses a Client (1937), aka: Dumb Witness
Death on the Nile (1937)
Dead Man's Mirror (1937)
Appointment With Death (1938)
A Holiday for Murder (1938), aka: Murder for Christmas
The Regatta Mystery (1939)
Sad Cypress (1940)
The Patriotic Murders (1940)
An Overdose of Death (1940), aka: One, Two, Buckle My Shoe
Evil Under the Sun (1941)
Murder in Retrospect (1943), aka: Five Little Pigs (1942)
Murder After Hours (1946)
The Labours of Hercules (1947)
There is a Tide (1948), aka: Taken at the Flood 
Witness for the Prosecution & Other Stories (1948)
Mousetrap & Other Stories (1950)
The Underdog and Other Stories (1951)
Mrs. McGinty's Dead (1952) Poirot / Ariadne Oliver
Funerals Are Fatal (1953), aka: After the Funeral
Hickory, Dickory, Death (1955)
Dead Man's Folly (1956) Poirot / Ariadne Oliver
Cat Among the Pigeons (1959)
The Adventure of the Christmas Pudding (1960)
Double Sin and Other Stories (1961)
The Clocks (1963)
Third Girl (1966) Poirot / Ariadne Oliver
Hallowe'en Party (1969) Poirot / Ariadne Oliver
Elephants Can Remember (1972) Poirot / Ariadne Oliver [see review]
Hercule Poirot's Early Cases (1974)
Curtain (1975)

Agatha Christie: The Superintendent Battle Mysteries

Main Character: Scotland Yard's Superintendent Battle. To be accurate, Superintendent Battle is not so much a main character as he is a unifying element in this series of books. He also appears in the Hercule Poirot mystery, Cards on the Table.
Setting: England
Bold type indicates a book I've read.

The Secret of Chimneys (1925)
The Seven Dials Mystery (1929)
Murder is Easy (1939), aka: Easy to Kill
Towards Zero (1944), aka: Come and Be Hanged