One who sleeps after sating himself with Torah, will not receive bad news in a dream: Berachot 14a
A good dream cannot come while one is sad, lazy, clowning, light-headed, or involved in wasteful things; only while one is involved in the joy of a Mitzvah: Pesachim 117a
Dreams as a Means of Communication between Hashem and the Jews during Periods of Divine Hiding: Chagigah 5b
Communication with the Dead in a dream: Shabbat 152b; Moed Katan 28a
All dreams contain some emptiness in them: Nedarim 8a-b
Rabbi Elazar saying, "I saw Rabbi Yochanan in a dream, and so I knew that I was going to teach a correct idea that day": Bechorot 5a