I used this Wikipedia page as reference, manually searching for each title entry on Amazon. I didn't search each title on Netflix because its more robust recommendation features kept suggesting the same small batch of titles, leading me to believe I had about found all it had on offer. Anyway, Amazon Instant has a massive, Viking-king vault treasury full of these things free to stream. I've organized links to each of the available titles below in the chronological and series order used by the Wikipedia page. I've modified chronology in favor of IMDB release years, which reflect original international release rather than favoring the U.S. release date. I've made a few additions myself, as well.
Click on the titles to be taken to the relevant Amazon Instant or Netflix page! Or read the Wikipedia page to read the fascinating history of this film craze! Don't stay too long in the desert! Or do!
1958 - Hercules
1959 - Hercules Unchained
1960 - Goliath and the Dragon
1961 - Hercules in the Haunted World [NETFLIX]
1962 - The Fury of Hercules
HERCULES DUBS:
1963 - Hercules Against the Mongols
1964 - Hercules Against the Moon Men (MST3K)
MACISTE SERIES:
1960 - Colossus and the Headhunters
URSUS:
1961 - The Vengeance of Ursus
1963 - Ursus in the Land of Fire
THE SONS OF HERCULES TV SERIES:
NON-SERIES ITALIAN PEPLA:
1959 - Devil's Cavaliers
1959 - Herod the Great
1960 - Cleopatra's Daughter
1960 - Conqueror of the Orient
1960 - David and Goliath [NETFLIX ONLY]
1960 - Esther and the King
1961 - Amazons of Rome [NETFLIX ONLY]
1961 - Constantine and the Cross
1961 - Duel of Champions
1961 - Duel of the Titans [NETFLIX]
1961 - Last of the Vikings
1961 - My Son, The Hero [NETFLIX]
1961 - Romulus and the Sabines
1962 - Damon and Pythias
1963 - Thor and the Amazon Women
1964 - Giants of Rome
1964 - Gladiators Seven
1964 - Lion of Thebes
1964 - Sandokan, Pirate of Malaysia
1964 - Saul and David
1964 - Two Gladiators
1965 - Challenge of the Gladiator
1965 - Kindar the Invulnerable
1966 - Knives of the Avenger [NETFLIX ONLY]
1978 - The Norseman [NETFLIX]
NON-ITALIAN MOVIES:
1945 - Caesar and Cleopatra [NETFLIX]
1949 - Samson and Delilah
1953 - Julius Caesar
1953 - The Robe
1956 - Alexander the Great [NETFLIX]
1958 - The Vikings
1959 - Solomon and Sheba [NETFLIX]
1965 - The Agony and the Ecstasy [NETFLIX]
1966 - The Bible
LATER MOVIES:
1984 - Conan the Destroyer [NETFLIX ONLY]
2011 - Conan the Barbarian [NETFLIX]