Just what I needed

I was apprehensive after reading the latest reviews, but this plugin works great for what I needed, which was to restrict the Contributor role to posting in specific categories. When a Contributor clicks Posts > Add New, only the categories I selected are available to choose from in the Categories metabox.

I’m not sure if the plugin is suppose to limit showing just the user’s own posts under Posts > All Posts and on the dashboard Activity widget (it doesn’t), but if that’s a concern, try adding the following code to your theme’s function.php:

function query_set_only_author( $wp_query ) {
    global $current_user;
    if( is_admin() && !current_user_can('edit_others_posts') ) {
        $wp_query->set( 'author', $current_user->ID );
        }
}
add_action('pre_get_posts', 'query_set_only_author' );