Tia Dalma

Tia Dalma is a character from the movies Pirates of the Caribbean: Dead Man's Chest and Pirates of the Caribbean: At World's End, played by Naomie Harris. She seems to be a practitioner of Voodoo, and is an associate of both Captain Jack Sparrow (Johnny Depp) and Captain Barbossa (Geoffrey Rush).

Pirates of the Caribbean: Dead Man's Chest
Tia Dalma is a voodoo priestess who traded Captain Jack Sparrow his famous compass seven years prior for a bag of gold (as told in Disney Adventures). In Pirates of the Caribbean: Dead Man's Chest, Sparrow seeks Dalma's assistance for information about Davy Jones and the Dead Man's Chest. In exchange, he gives her Jack, Barbossa's cursed monkey. She later provides shelter and comfort for the surviving Black Pearl crew after the Kraken destroys the ship and takes their captain. It is Tia who proposes sailing to the World's End to rescue Jack; but first she reintroduces the still living Captain Barbossa to the stunned survivors. Fans speculate along with her being Davy's lover, of being Calypso, goddess of the sea. A locket can be seen in Dead Man's Chest when the crew of the Black Pearl first arrive at Tia Dalma's hut. When she goes into the back room, it shows Jack Sparrow picking a ring off the table and the locket can be seen. This locket has a striking resemblance to the face of the lock on the actual Dead Man's Chest, a crab seen from above in the shape of a heart and in Davy Jones Ship by the Organ when Will took the key from him.

Pirates of the Caribbean: At World's End
In an interview by FilmFocus, Naomie Harris reveals that Tia Dalma will journey with the Black Pearl's crew to the World's End. She is, "...not really who she says she is. She is a lot more powerful." It is hinted that she and Davy Jones were past lovers and that Dalma is the sea goddess Calypso. She also hints that they will have a relationship in the movie.

The trailer does not show much of Tia Dalma, all that is known is that she and Barbossa are guiding the others to where Jack is.

It's hinted that Tia Dalma and Jack Sparrow were once romantically involved, based on Sparrow's apprehensiveness over seeking her assistance and his reaction to her flirtations with William Turner. Although the exact nature of their relationship is unknown, in an interview with Naomie Harris, she says that Jack Sparrow and Tia Dalma probably were lovers. It is also thought that Barbossa and Tia Dalma are going to have an affair in the movie..

Trivia

 * Tia Dalma's name is an anagram of Dalmatia. The Dalmatian Coast was a historical haven for pirates - once known as the Roman province of Illyricum and before that the kingdom of Illyria. Illyria was a pirate kingdom - plundering Roman and Greek vessels in the Adriatic - ruled by the pirate queen, Queen Teuta.
 * Tia Dalma's firefly-surrounded dwelling is a homage to a small shack seen at the beginning of the famous Disneyland ride.
 * Fans have noted similarities between Dalma and the Voodoo Lady of Monkey Island series of games. They point out similarities also between their hut interior, as well as the landscape they are located (both in bogs and swamps)
 * Jack the Monkey's sudden good behaviour in Tia Dalma’s house foreshadows Captain Barbossa's presence, further illustrated by Jack perching atop a pair of boots of an unseen individual in the room adjacent to the protagonists during their visit.
 * Tia Dalma's theme (as heard on the soundtrack) contains many motifs from Barbossa and the Haunted Pirates' theme song from the first movie, which may foreshadow her hand in his resurrection. In addition, her theme contains several parts which are played by a music box like machine, similar to Davy Jones' theme, and contains motifs (including the main motif) from his theme as well, also suggesting a connection.
 * In the young Jack Sparrow books, she is mentioned to have turned a girl named Constance into a cat. It is also revealed that Jack has known her since he was a child. However, in the movies, she appears younger than Sparrow (although not as young as Will and Elizabeth), this might be further evidence to her as-of-yet-unknown powers- not aging, or simply delaying the process.  He also calls her "Mommy dearest" in the seventh book.
 * Tia Dalma's in-depth knowledge of Davy Jones' origin, as well as her personality and her surety, and indeed passionate description, that it was a woman Davy Jones fell in love with, and not the sea, could indicate that she is the "changing, harsh, and untameable as the sea" woman that Davy Jones fell in love with.
 * While Jack steals a ring from Dalma's hut, we see a necklace with the same shape as the music box that puts Jones back to sleep when Will is stealing the key, also the same shape as the area where the key goes in on the Dead Man's Chest may also hint a connection between Davy Jones and Tia Dalma.