Blogs are personal or course-based journals that are meant to be shared with other members of the class. Anyone in the class can comment on postings.
Wikis are a public space where students can work on a document collaboratively and the entire class can see and contribute to the content.
Journals provide a space for reflection. This tool can be used as a private space for assignments where students are expected to write and allows for comments from the teacher.
Each of these tools can be graded and can also be restricted to Blackboard "groups".