Not a complete list, but this has a lot of cut content:
Deadeye Duncan on Manaan
The Taris arena fighter Deadeye Duncan survived the events of the planet and would show up on Manaan.
He reveals that he's trying to become a mercenary and is finding it hard to find work due to his reputation. He asks your character if he can use your "Mysterious Stranger" name as a way to fix his reputation.
Sith Board The Ebon Hawk
After deciding who would rescue you, Carth and Bastila on the Leviathan, there was supposed to be a quick cutscene where Carth, Bastila, and the PC are shown being taken prisoner by the Sith boarding party.
Alternative Darkside Female Ending
In order to make the deadline for this game, an alternate ending for dark side females was cut.
The ending took place when Carth comes to the Star Forge to speak to you one last time. From there you could choose to redeem yourself by killing Bastila and stop her using her battle meditation on the sith forces. However, in doing this, the player and Carth lose precious time in escaping from the Star Forge and remain on the Star Forge as Republic forces destroy the Star Forge.
Black Vulkar Base Expansion
An extension of the Taris Swoop Bike quest, in which a second level exists in the Vulkar base and the player has to disguise himself as a Vulkar to infiltrate it.
Rulan Prolack Expansion
In the fight with Rulan Prolack (the shape changing alien you're sent to kill for the GenoHaradan), he always transforms into Jolee. However it seems he was at one time meant to transform into any one of your NPCs, even your PC.
Alternative Way Into Taris Sith Base (tar_m02ad)
There was an alternate way into the Sith base on Taris. The junior Sith officers you meet in the cantina could later be talked to at the party for a chance to buy a passcard into the base. (this only needs me to sort out a script then it's done)
Indecent Proposal
As a "reward" for rescuing Shen and Rahasia, the PC had the option to make an... indecent proposal (Shen for female PC, Rahasia for male) shortly before Ahlan and Nurick show up.
Garrum and Tareelok
An argument between a Master and his apprentice was supposed to take place on Dantooine.
Manaan Pazaak Tournament
You could compete in a Pazaak tournament on Manaan.
Sith Patrol In Sewers
The Sith patrol you meet in the Undercity was at one time in the sewers (or possibly it was a second patrol) and were much harder to fool (you'd have to show your papers and then pass a persuade check).
Carth's Extended Taris Apartment Dialog
A little bit of unused dialogue near the beginning, Carth tells the PC to go back to sleep until their injuries heal.
The Echani Mercenary's Friends
During your adventures on Manaan, you could partake in a side quest to find out what happened to an Echani mercenary's friends.
The PC fights alongside Jolee
More bits of dialogue seem to suggest that Jolee and the PC were meant to fight together in the Shadow Lands before he officially joined your party. Perhaps against the Katarns you see him kill?
Swoop Bike Parts
A possibility to buy parts for the Swoop Bike. On the Swoop Track on Tatooine, when the player talks to a racer named Nico, he can still ask Nico where there's a place to buy upgrades for the swoop bike. Bioware forgot to cut this dialogue.
Belaya Captured
If the player didn't kill Juhani, the Jedi Belaya, from the Jedi Enclave on Dantooine, was supposed to have been captured and kept as a prisoner aboard the Leviathan. She would later be discovered to have died in captivity.
Canderous and Juhani's Talk
As with other team configurations, if Juhani and Canderous were part of the player's team, they were supposed to have dialogue with each other. Specifically about the Mandalorian invasion of Cathar.
Dungeon on Tatooine
An alternate Star Map scenario where the map is located in the maw of a Sarlacc. The player must navigate an underground Rakatan temple in order to locate the pit, and then figure out how to get to the map without getting eaten.
Sewers Trash Compactor Puzzle
A trash compactor puzzle in the Taris Sewers.
Sand People Messiah
A quest that would have allowed the player to become a sort of Messiah of the Sandpeople and lead them against their Czerka corporation oppressors.
Gammorean Stronghold
A Gammorean stronghold used to exist in the Taris Undercity.
Carth/Female Revan Extended
An extended romance .dlg for Carth with a Female Revan, for a better executed beach scene.
Shuma The Hutt
Shuma the Hutt originally could be found in the Jedi Enclave. Due in part to recent events, Shuma was granted asylum in the Enclave.
Iriaz
Passive Iriaz originally roamed the plains of Dantooine. That's right, other creatures roamed the plains and didn't attack you on sight.
More Swoop Races
You could go swoop racing on Kashyyyk, Dantooine and Korriban
Extended Shadowlands
A third area of the Kashyyyk Shadowlands could be accessed (it is a lower level beneath the second level and some of the areas were created but are mostly empty, with very little content in them).
Sunry Murder Expansion
Apparently it was possible that Revan could discover a datapad written by Elassa to her Sith Master shortly before her death, inside the Sith Embassy. In it she says that she doesn't believe Sunry knew anything of value, and actually intended to murder him on the very same night the jilted Sunry killed her. Ironically, while Sunry had killed her in cold blood, he had unknowingly prevented his own death at the same time.
Bastila on Korriban
Bastila was originally allowed to accompany you during your trip to Korriban. This is evidenced by dialogue and voices that still exist in the game files.
Juhani's Leviathan Dialogue
Juhani had some dialogue after you escape from the Leviathan.
Party Dialogue for Korriban Star Map
It appears as though nearly every one of your NPC teammates had something to say after you find the Star Map in Naga Shadow's tomb. However, as we all know, only your character is allowed to enter Naga Shadow's tomb.
Juhani Speaks of Korriban's Evil
You could speak with Juhani after finding the Star Map on Korriban. The dialogue itself involves Juhani telling you of her dislike of Korriban's evil and how it affected her.
Juhani Dislikes Canderous
You could speak to Juhani about why she dislikes Canderous. The dialogue itself obviously became available shortly AFTER her argument with Canderous.
Taris Lower City Extended
There was more content for the Taris Lower City orginally such as a way into the swoop track and more Black Vulkars that would attack.
Juhani Speaks More of Taris
Shortly after you learn that Juhani's last home planet was Taris, you could talk to her again to learn about how the prejudice and racism of other people affected her life on Taris.
Carth's Devastation
Originally, if you had been doing the Carth romance sidequest, a dialogue with Carth revealed he was much more devastated with your character being Revan than he was in the final version of the game.
More Juhani Dialogue
Juhani had additional comments about Revan.
Sharina Fizzark
Sharina Fizzark, the woman who tries to sell you the great wraid plate on Tatooine, can later be found on Dantooine building a new life.
Dantooine Burial Mound Expansion
Apparently you had to do some extra work if you wanted to enter the burial mound on Dantooine as evidenced by a sound file of Bastila talking about how to open it.
The PC threatens a Sith Commander on the Leviathan
Your character at one point in the game could threaten or ask a Sith commander on the Leviathan to help you.
Injured Dark Apprentice
At one point, you encounter an injured dark apprentice in the Rakatan Temple on the Unknown World.
Canderous and Juhani dialog
Due to a small glitch in a dialogue file Bioware forgot to fix, conversation between Juhani and Canderous that takes place on Kashyyyk is never heard in the final version of the game.
Some Jawa NPCs were apparently cut from Tatooine.
A lightsaber crystal called Wookie amulet was cut from the game
There were three additional difficulties Very Easy,Hard,and Impossible (Impossible is the only one that can be safely restored)
There was originally more to the tar-preraid cutscene with Carth chiming in and some dlg choices for the PC.
Zaalbar has some dialogue in the Shadowlands.
The off-duty Sith in the Taris Cantina has some cut dialogue for the opposite gender
Guard Stance was a cut feat
The Glow Rod was cut from Taris
Krayt Dragon Fight
You could fight the Krayt Dragon on Tatooine