There are 7 Sages in Ocarina of Time. Zelda is one of them. Here they are:
Warning: there are spoilers!
The Sages
Saria
Saria is the first sage you meet, but she isn't a sage at first. Link and Saria are great friends. It is obvious they like each other, but Mido is always trying to hit on her. She becomes the new Sage of Forest later.
Zelda
Zelda is the Leader of the Sages. I am not going to tell about her. Go to my Characters post to read about her.
Rauru
Rauru is the Sage of Light. He is the first sage that knows he is a sage that you meet. He is the one who keeps Link in the Temple of Time for 7 years. He also gave him the Light Medallion.
Darunia
Darunia is the Goron leader and the Sage of Fire. He locks himself in his room with the Goron Ruby until Link comes and plays Saria's Song. He tells Link to fight the monsters in Dogondo Cavern and gives him the Goron Bracelet. After beating King Dogondo, Link is given the Spiritual Stone of Fire. Later, after beating Volvagia, he gives Link the Fire Medallion.
Princess Ruto
Princess Ruto is the Sage of Water. After going into Lord Jabu-Jabu, Link finds her and they go to search for the Zora's Sapphire, but during a fight with a Big Octo, Link loses sight of her. She gives him the Zora's Sapphire (they found it earlier), and considers them married because the Sapphire acts as the Zora's Engagement Ring. After Link's 7 year sleep, he returns to the Zora realm, and finds all but Princess Ruto (she was rescued by Sheik) covered in ice. When Link beats Morpha, he finds out Ruto is the new Sage of Water. She tells him that their "engagement" must be called off because of her duty as a Sage, and gives him the Water Medallion.
Impa
Impa is the Sage of Shadow and Zelda's Nanny. She teches Link Zelda's Lullaby, turns Zelda into Sheik, and goes to the Shadow Temple so she can lock up Bongo Bongo. Link follows her and succeeds in defeating Bongo Bongo, awakening Impa as the Sage of Shadow. She gives Link the Shadow Medallion.
Nabooru
Nabooru is the Sage of Spirit and leader of the Gerudo. Link meets her in the Spirit Temple. She doesn't like Ganondorf, so she went to the temple to disrupt his plans. Unfortunately, she needs the Silver Gauntlets, which are out of her reach. Link got the Silver Gauntlets but was not able to give them to Nabooru, because she had been captured. 7 years later, Nabooru was brainwashed. Link finds her as an Iron Knuckle and frees her, awakening her as the Sixth Sage. She gives Link the Spirit Medallion.
More coming later, see ya!