Umbraco CMS and DevCore as developers
Umbraco is a flexible, user-friendly and fully-equipped .NET Content Management System CMS designed to easily publish material.
No hassle, no restrictions. Umbraco offers a framework that doesn’t stand in the way for what you need to do. It can drive any kind of CMS project - from a small web campaign to some of the largest webpages in the world. Umbraco let you create creative and powerful layouts using blocks, crop and format images, move and sort objects with drag and drop.
Umbraco is called the world's friendliest CMS
Umbraco has a large and active community of companies and developers, and it is growing all the time, it is one of the world's largest Open Source CMS tools.
There are a wide range of extensions and plug-ins. There are more than 300 free add-ons for Umbraco, which you could start using immediately. They maintain high quality and the interface is full of smart features. It's easy to see how the page looks like on the cellphone, ipad and on the web, for example. Chances are that an idea for something one wants to build, already is built because it is based on open source.