Mac: You can stream audio and video easily over AirPlay, but you need an AppleTV hooked up if you want to watch or listen to your media on a television. SofaPlay offers the same functionality, but with the more widely implemented UPnP/DLNA standards.
If you have a gaming console or modern flatscreen television set, chances are you have a UPnP/DLNA-capable device. Just open up the app, drag the media you want to play, and select where you want to stream it from the device list. SofaPlay will take care of everything else and send the file over to your TV.
Controls to scrub through the file and mute audio are available, plus you can replay recently used media files through a list you can access in the main panel.
If you want to give it a try before you buy, you can download the "lite" version for free and stream anything for up to two minutes.
SofaPlay ($5.49) [Mac App Store]