WooCommerce - dequeue css (2.1+)

functions.php

// Remove each style one by one
add_filter( 'woocommerce_enqueue_styles', 'jk_dequeue_styles' );
function jk_dequeue_styles( $enqueue_styles ) {
	unset( $enqueue_styles['woocommerce-general'] );	// Remove the gloss
	unset( $enqueue_styles['woocommerce-layout'] );		// Remove the layout
	unset( $enqueue_styles['woocommerce-smallscreen'] );	// Remove the smallscreen optimisation
	return $enqueue_styles;
}

// Or just remove them all in one line
add_filter( 'woocommerce_enqueue_styles', '__return_false' );