BuddyPress.org

Presume that you actually mean – “so they *can* blog” ?

Can you not simply set the ‘new user default role’ to ‘Contributor’ or ‘Author’ in general settings then all your users can post to the main blog.

If that isn’t what you’re after then you’ll need to elaborate a little on what you are actually wanting to do i.e allow them to post from the front end of the blog without having to use the dashboard?