Plex is a free media server add-on developed by Plex, Inc. that is compatible with many devices, including Chromecast, Xbox, PlayStation, Android, Apple, Roku, Fire TV, and more. It is used for media streaming and organization.
Emby is a powerful tool that allows you to keep your personal videos, music and photos and stream them to your devices. The app lets you share your files with friends and family, watch Live TV and manage your DVR.
Stremio is a video streaming aggregator that lets you watch, organize and discover movies, TV series and video channels. The content is compiled by an add-on system that provides streams from Netflix, iTunes, HBO, YouTube, Twitch and other services.
CEMC (Community Edition Media Center) is an open source media center that allows you to keep your videos, programmes, movies and music in one place. You can install it even if you have other media center, because it will not interfere.