WebP is a image-format - developed by Google - aimed to reduce the size of images dramatically. While still in development, WebP-images already allow you to reduce the size of JPG or PNG images. Unfortunately, the WebP image-format is at this moment only supported by a small number of browsers.
Google reCAPTCHA is popular, but requires various steps to be implemented in Magento. This extension saves you time, and offers you a clean integration.
The New Relic service offers professional monitoring of your site and server performance. When analyzing Magento performance, this could prove vital.