Stop WooCommerce.com nag

gistfile1.txt

add_filter( 'woocommerce_helper_suppress_admin_notices', 'jmg_woocommerce_helper_suppress_admin_notices' );

// Don't show the 'Connect your store to WooCommerce.com to receive extensions updates and support.' nag
function jmg_woocommerce_helper_suppress_admin_notices( $default ) {
    return true;
}

I always forget about the WordPress __return_true() helper function. A cleaned method as posted by Marco Almeida is:
add_filter( 'woocommerce_helper_suppress_admin_notices', '__return_true' );