Using WooCommerce Simple Checkout
You'll need a copy of WooCommerce Simple Checkout to proceed with this guide. You can get the plugin here.
Once you have activated the plugin WooCommerce will hide all address fields on the checkout page for orders with only Virtual products in them.
To simplify the checkout page for orders with virtual items all you need to do is set the relevant products to be a virtual product.
The plugin has no settings.