XBMC is a media center app that runs on many different OSes, including OS X. The current release (12.0 - Frodo) offers several new features, including HD audio support, DTS-MA, and Dolby True-HD. Also new is the ability to use XBMC as a PVR (personal video recorder), which lets you watch live TV, schedule recordings, and view a TV guide.

XBMC
XBMC also supports many remote capabilities, and includes a handy app that turns your iOS device into a remote control.
XBMC has a lot of features and capabilities. Setting up some of the services available in this media center isn't for the faint of heart, but XBMC can still be an excellent choice if you're a home theater devotee who wants to put together a custom entertainment system using Macs and iOS devices.
XBMC is free. Donations are encouraged to help support development.
See other software choices from Tom's Mac Software Picks.

Just installed XBMC on my MacBook Pro, I’m a complete novice, but it really is quite simple. The best way to add add ons is to install fusion in program’s, a guide is on XBMC’s website.
A very neat clever program for free.