You can easily display most recent blog posts across your WordPress Multisite Installation including recent posts from all subsites and main site of your WordPress Multisite Network.
All you need to do is install and activate Network Latest Posts. Upon activation visit Dashboard -> Appearance -> Widgets page and drag drop its widget to your sidebar or anyother widget area. This widget can be used on both main and subsites of your WordPress Multisite Network.
You can also use its shortcode generator for displaying network wide latest posts inside your page, post or custom post type.
The plugin works same as the old Multisite Recent Posts Widget plugin, this plugin is its latest version which provides you more advanced features and is compatible with the newest WordPress update of 3.5.1