Curse Of The Blood Rubies
Where it Fits - This movie is a spin-off/an alternate opening and introduction to the series and gives a different outcome of events compared to the show. It starts off with a different way in which Bulma and Goku meet each other, and then carries it onto a different path from the series thereafter.
The Path To Power
Where it Fits - This film is also another spin-off, retelling the events of Goku and Bulma meeting each other and what follows after. It was made in honor of the 10th anniversary of the Dragon Ball franchise.
Sleeping Princess in Devil's Castle
Where it Fits - This film retells the events of the way that Krillin and Goku went to Master Roshi to receive their training and follows what happens throughout, if it fit into the show's timeline then it will be immediately at the end of The Sage Of Goku, right after episode 13 (Goku's Great Transformation / The Legend of Goku).
Where it Fits - It is almost a sequel to the previous film, thereby is not a part of the main timeline, and so retells the story of the events that followed Goku and Krillin's training with Master Roshi when they finish, however if it fit into the show's timeline it would be during the Tournament Saga, right after Episode 18 (The Turtle Hermit's Intense Training / The Turtle Hermit Way).
Goku's Traffic Safety and Goku's Fire Brigade
Where They fit - The films are public service videos that used the Dragon Ball characters to promote traffic safety and caution when using fire.