Do you make a blog primirily for your site? Such as a update blog or a status blog.
If you dont know an update blog will announce updates for your site
A status blog is like what your status is the "yeah we screwed up, give us a minute" blog.
Depends on what kind of forum you are running. A webmaster forum or a forum about a specific topic (like breast cancer or bee keeping or whatever), it would be a good thing to have. That way you can store informative articles for your members to refer to when they wish.