Summary: Although discussion boards can enhance interaction within a course, some guidelines may help you organize your discussion boards for increased interactivity.
You should carefully define the discussion assignments, defining requirements and expectations. Discussion board rubrics and model postings are helpful to structure the activity for students.
A word here about group projects and grading. There is a lot of controversy about the best way to assign grades for group activities. This comes back to the issue of students feeling that some students did not contribute as much as others. We have found that a group grade on the product and a group self-evaluation on group participation is useful. Students individually submit a group contribution form at the end of the assignment that details their perception of participation in the group. Students are also told that the group's responsibility is to inform the instructor when someone on the group is not contributing according to the expectations of the group. The instructor can contact the student via email (after ensuring that the group has documented evidence of their attempts to engage the student) and pose a simple choice - contribute to the group work or do the entire assignment individually. Most students conform quickly. Another variation to this technique is to have students name the group members who contributed the most to the assignment. You might consider providing some extra points for members who are great contributors.