Open Source CMS
Drupal CMS has gained market share every year for nealry the last 10 years and we have been using Drupal since it's first introduction, it's open source which means there are no royalty fees or expensive licenses to pay for reducing the cost considerably both in initial purchase and long term cost of ownership.
Drupal has a huge well organised community keeping the CMS up to date and moving forward in line with the latest innovations in technology.
The data layer, business logic and presentation layer are kept apart and it's modular design make it very flexible and can accomodate virtually any requirement.
It 's modular design means different user intrfaces (themes) can be used and even different template engines. It's functionality resides in various modules which aids customisation and easier bespoke development.
Drupal's considerable codebase expands daily, there are a choice of off the shelf modules allowing integration with social media such as Facebook and Twitter. It can be used with conjunction with virtually every internet technology around today and in the future, whether you're acessing a SOAP api and dowloading JSON data or getting the latest weather data from Yahoo drupal has a way of getting the job done.
By far the majority of drupal installations sit on an Apache web server whilst connected to a MySql database it can also be run from any webserver that supports PHP. That could be ngnix or Microsoft.
It's not limited to MySQL for it's core database, if you need a larger data requirement then it can work with Microsoft SQL Server or Oracle and most major databases.