// initialise widget
function sjc_silo_widget_init() {
    if ( function_exists( 'wp_register_sidebar_widget' ) && function_exists( 'wp_register_widget_control' ) ) {
        wp_register_sidebar_widget( 'sjc_silo_latest_widget2', 'Latest Silo Posts', 'sjc_silo_latest_widget' );
    }
}
add_action( 'plugins_loaded', 'sjc_silo_widget_init' );

// create widget
function sjc_silo_latest_widget( $args ) {
    $sidebar_category = get_the_category();
    // if we have a category and we're on a normal post / page / cpt page call the function
    if ( $sidebar_category[0] && ! is_front_page() && is_single() ) {
        extract( $args );
        sjc_silo_latest_content( $sidebar_category[0], $before_widget, $after_widget );
    }
}

// echo the sidebar - called by widget, can also be called directly
function sjc_silo_latest_content( $this_sidebar_category = null, $before_widget = null, $after_widget = null ) {
    global $post;
    if ( ! empty( $this_sidebar_category ) ) :
        $posts_in_this_category = get_posts( 'category__in=' . $this_sidebar_category->cat_ID . '&exclude=' . $post->ID );
        if ( count( $posts_in_this_category ) > 0 ) { ?>
            <?php echo $before_widget; ?>
            <h2 class="widget-title">Latest from <?php echo $this_sidebar_category->cat_name; ?></h2>
            <ul style="margin-bottom:10px;">
            <?php foreach ( $posts_in_this_category as $sidebar_value ) : ?>
                <li><a href="<?php echo get_permalink( $sidebar_value->ID ); ?>" title="<?php echo $sidebar_value->post_title; ?>"><?php echo $sidebar_value->post_title; ?></a></li>
            <?php endforeach; ?>
            </ul>
            <a href="<?php echo get_category_link($this_sidebar_category->term_id ); ?>">More from <?php echo $this_sidebar_category->cat_name; ?></a>
            <?php echo $after_widget; ?>
        <?php
        }
    endif;
}