In Surprise, Buffy had a dream that predicted her losing Angel. She lost him as Angelus.
In Faith, Hope and Trick, she had a dream of dancing with Angel. The ring he gave her slipped off her finger and fell to the floor. At the end of the episode she placed the ring on the floor at the spot where she sent him into Hell and said goodbye to him. A little bit later, Angel was returned, right there.
In Graduation Part II, Buffy had a dream where Faith told her the Mayor's weakness so she could defeat him. In that same scene, this line was said by DreamFaith:
"Miles to go, little miss muffet counting down from 7 3 0."
Little Miss Muffet = Dawn.
Reasoning: The first crazy guy who saw through the Key said, "I know who you are. Curds and way."
7 3 0 = Restless (the First Slayer trying to kill the Scoobs in their dreams)
Reasoning: 730 days equal 2 years exactly (365+365). The season 4 finale was two years after the graduation episode.
In Hush, she dreamed of the Gentlemen and how to defeat them, as well as Riley, and the connection between Riley and Professor Walsh (the 'be a good boy' reference). Riley also said, "If I kiss you, we can make the sun go down." If that was relevant is unknown.
In This Year's Girl (S4) Buffy had a dream with Faith in it again. In this one Faith said, "Little sister's coming. So much to do before she gets here."
Again, predicts Dawn.
In Restless, she saw the clock in her room reading 7:30.
Also in Restless, the following things were prophesied and have occurred. Theories for the future are left out for now.
1) Tara's "secret" (during Willow's Dream)
2) The Musical Episode (during Willow's Dream)
3) Willow's possible changes (during Willow's Dream)
4) Spike and Giles thinking they are father and son, and the loan "shark" from Tabula Rasa (Xander's Dream)
5) Giles' leaving (Giles' Dream).
6) Spike's posing as a 'Big Bad'. (Giles' Dream)
7) Dawn's appearance. (Buffy's Dream)
8) Joyce's death (Buffy's Dream)
9) Riley's departure (Buffy's Dream)
Special Note: In Season 5, Buffy didn't have a single dream like this. Coincidence?