Blog Customization - users may customize their blogs in the same manner that they can customize their user profiles (introduced in 3.7).
Group Blogs - users may allow other users to post to their blog.
Sidebar Blocks - users may create custom blocks to display in their sidebar. These blocks can be rearranged by drag and drop.
Custom Pages - users may create custom pages to be displayed in their blog.
Tags - tag support has been included.
Featured Entry Manager - multiple entries can be featured on the blog home page now.
Private Entries - users may set specific entries to be private while leaving their blog open.
Admin Categories - admins may define categories now.