Transcipts of each episode of "Buffy" can be found at The Slayer's Fanfic Archive (aka Slayerfanfic).
A more complete quote section can be found at Domain of the Slain.
Quotes -- These are just a few of my favorite quotes.
Season One Season Two Season Three
Welcome to the Hellmouth & The Harvest
The Witch
Teacher's Pet
Never Kill a Boy on the First Date
The Pack
Angel
I,Robot--You, Jane
The Puppet Show
Nightmares
Invisible Girl
Prophecy Girl
When She Was Bad
Some Assembly Required
School Hard
Inca Mummy Girl
Reptile Boy
Halloween
Lie to Me
The Dark Age
What's My Line (Part 1)
What's My Line (Part 2)
Ted
Bad Eggs
Surprise
Innocence
Phases
Bewitched, Bothered, and Bewildered
Passion
Killed by Death
I Only Have Eyes for You
Go Fish
Becoming (Part 1)
Becoming (Part 2)
Anne
Dead Man's Party
Faith, Hope, and Trick
Beauty and the Beasts
Homecoming
Band Candy
Revelations
Lover's Walk
The Wish
Amends