Discussion boards
Blackboard provides an online "discussion board". Using this feature, faculty or students can post a question, and have other in the class respond and participate in a discussion - at any time of the day or night and without the need to be in the same room at the same time.
This link will take students to a set of tutorials for commonly used features in Blackboard. Feel free to enter it into your course:
http://breeze.quinnipiac.edu/studenttutorials/