Listen to this morning's class, "Can Dreams Determine Halakhah?" here.
Follow along with the sources here.
For further research:
1) Read Prof. Israel Ta-Shma's "שאלות ותשובות מן השמים" here.
2) Read R. Dr. Ephraim Kanarfogel's "Dreams as a Determinant of Jewish Law" here.
3) Read Prof. Pinchas Roth's "Responsa from Heaven" here.