Drupal is a multi-awarded CMS being used by many global organizations. It has a powerful framework which allows building a simple brochure website up to a large multi-country content portal.
Magento is one of the most popular and highly regarded shopping cart software today. Mainly because it offers a lot of great e-commerce features that is already built-in to the package of the software.
WordPress is the platform of choice by most website owners, web designers and web developers alike for being very easy to use and having a framework that is very easy to build and maintain.