Removal of Link Manager / Blog Roll
If you have upgraded from a version before WP 3.5, you may still have the link manager in the sidebar, although it is not needed. To remove this, edit the "Link Manager Enabled" field from 1 (on) to 0 (off) in /wp-admin/options.php or via the database under wp_options.
An alternative way is to add this code to your functions.php file:
update_option( 'link_manager_enabled', 0 );
If you regret, you can re-enable the link manager by adding the following line to your theme's functions.php file:
add_filter( 'pre_option_link_manager_enabled', '__return_true' );