I am brand new to WordPress and trying to set up a family research site. I signed up at WordPress.com and I'm just discovering the world of WordPress.org. I want to do essentially the same thing you were describing: Have my blog in the main body, but also have a sidebar that shows the latest activity on a forum on the main page of my site. Readers can read my latest message on the blog, but can interact with me and other readers on the forum, rather than posting themselves to the blog and commenting that way. I then want users to be able to search the forum to help them further their own research.
What did you discover about this? Do you have to just use a plug in and put a forum on a separate page? Or would what I'm trying to accomplish work with just having everybody be able to post and comment on the same blog? Is there a way to make the forum look and feel like the WordPress themes? Is there away to pop in a forum that looks like the WordPress.org forums?