One of the most common objections I hear from instructors about teaching online is the lack of interactivity between students. The most popular tool in Blackboard for student to student (and instructor to student) interaction is the discussion board. I recommend considering the blog and journal tools as well as they are also great ways for students and instructors to interact with each other.
The blog tool is best for student to student interaction. It allows students to submit entries (posts) consisting of text, links, and images which can be commented on by other students. The blog can be setup as a graded assignment or as just an optional component of the course. One of the strengths of using a blog is that it encourage critical thinking without requiring the formality of turning in a formatted paper. Students can quickly type up and submit their views on a particular topic and then other students can comment with their own opinions. The blog tool also allows instructors to chime in with comments. Blogs in Blackboard can be a good alternative to using the often cluttered discussion board. Threaded discussions can be great, but the mix of threads and replies (and replies to replies) can make it difficult to evaluate a students writing in some cases. The simple appearance of a blog entry and comments is easy to read:
The journal tool is very similar to the blog tool but with the important difference that entries by students can only be viewed by the instructor (by default). Here is what a basic journal entry and comment from the instructor looks like:
Journal comments are limited to just the student who wrote the entry and the instructor. After the journal assignments have been graded, there is a setting that can be turned on which will allow students to read each others entries.
Blackboard has provided a few resources that will be helpful when setting up and using blogs and journals. Here are a few useful links:
Creating a Blog (video)
Commenting on a Blog Entry (video)
Creating a Journal (video)
Commenting on a Journal Entry (video)