Umbraco Umbraco is considered as WordPress competitor. and indeed it has huge community support and comes with lots of features, nicely documented, and video help is available.The only disadvantage seems its user interface, which is not as intuitive as it should have been. there is a nice discussion to go over before choosing Umbraco. Read more.
Pirana CMS Comes with lots of features as mentioned here. but it lakes demo website and admin interface. Greatest thing would be that it already uses MVC Framework 5 and Web Pages 3 and its compatible with web matrix (open source alternative of Microsoft visual studio). another good thing is its simple to understand for any ASP.NET MVC developer since it utilizes code ASP.NET MVC coding style.
Better CMS One of the best WHYSIWYG User interface. where a user can generate and publish content right on the website with few clicks. It has nicely written documentation but lacking free modules and themes to get started with. lake of community support as on APR-2014. But its backed by Devbridge Group and their Professionals.
kooboo Supports Multiple Sites, And ready for enterprise use. Has a forum to discuss ideas and issues. Kooboo has online demo website. but it seems it requires registration before the demo.
MrCMS Was launched in 2013 and then after rapid development, it has got a huge list of features, including Support for SQL Azure, and MVC5. But documentation is not yet complete. I believe the year of 2015 is going to be a year to polish Mr CMS and release documentation and help as possible. Good luck Mr. CMS.