Taboo
Description: A jinx which may be placed upon a word or a name, so that whenever that word is spoken, a magical disturbance is created that alerts the caster of the Taboo to the location of the speaker. Any protective enchantments in effect around the speaker are broken when the Tabooed word is spoken aloud.
Seen: In Deathly Hallows, this spell is placed on the word "Voldemort"; Harry, Ron and Hermione are tracked this way to Tottenham Court Road. Ron tells the other two to stop using the word as he began to fear the name might be a jinx, later discovering it to be a Taboo. The Taboo on Voldemort's name proves useful in identifying supporters of Harry Potter, since the name is so feared that only "rebels" dare speak it. Later in the book, Harry accidentally says Voldemort's name again, resulting in the trio being caught by Snatchers and taken to Malfoy Manor.

Tarantella Dance
Incantation: Tarantallegra
Pronunciation: tə-ran-tə-leg-rə
Description: Makes victim's legs dance uncontrollably, so the victim cannot control his or her movements.
Seen: First used by Draco on Harry in the Duelling Club in CoS. It can be stopped using Finite.

Tergeo
Incantation: Tergeo
Pronunciation: tur-jee-oh
Description: Siphons material from a surface, (e.g., blood, ink, dust, etc.)
Seen: Hermione uses this spell in HBP to remove blood from Harry's face, as well as to remove ink from an essay that Ron had completed previously. It was used in Deathly Hallows to clean off a handkerchief by Ron, and to dust off a picture of Gellert Grindelwald in Bathilda Bagshot's house.

Tongue-Tying Curse
Incantation: Unknown
Description: A curse that prevents certain information from being revealed by the individual upon whom the spell is placed. The curse manifests itself by causing the tongue to temporarily curl backwards upon itself.
Seen: Seen in Deathly Hallows as a deterrent to Snape, or any other unwanted visitor of Number 12 Grimmauld Place, from betraying their location to anyone else.

Transmogrifian Torture
Incantation: Unknown.
Description: Presumed to burn and contort the victim's body from the inside, killing them.
Extremely painful to the point where it's a surprise that none of the death eaters used them. Based on this we can say that a certain skill set is required to perform this curse and that people prefer the killing curse since the effect is quicker, more convenient, and most importantly, has no defensive spell or counterspell against it.
Voldemort is able to perform the curse but since he believed that there was nothing worse than death, perhaps he the instant death caused by the killing curse was better in his eyes.
Seen: Gilderoy Lockhart suggested that it was this curse that "killed" Mrs Norris after she was really found petrified on a torch bracket.

Trip Jinx
Incantation: Unknown
Description: Causes the victim of the jinx to trip and fall.
Seen: Used by Draco in OotP, to catch Harry when he was fleeing after the DA was discovered.