Serviio is a free media server. It allows you to stream your media files (music, video, or images) to renderer devices (e.g. a TV set, Bluray player, games console, or mobile phone) on your connected home network.
There is also a paid-for Pro edition which further enhances the possibilities of sharing content in your connected household.
Serviio works with many devices from your connected home (TV, Playstation 3, Xbox 360, smartphones, tablets, etc.). It supports profiles for particular devices so that it can be tuned to maximize the device's potential and/or minimize lack of media format playback support (via transcoding).
Serviio is based on Java technology and therefore runs on most platforms, including Windows, Mac, and Linux (incl. embedded systems, e.g. NAS).