If you have an Apple TV, you can stream video files from your Mac using AirPlay. Unfortunately, doing this requires iTunes, and the files in iTunes have to be a particular file format. Merlin Mann's pick on MacBreak Weekly 400 gets around these restrictions with Beamer 2.0 for OS X.
Beamer 2.0 works just like a regular media player, but it can stream the video over AirPlay to Apple TV. It works with any playable movie file, regardless of the format. You can create playlists so you can binge watch TV without interfering. It even will work with subtitles from BluRay or DVDs.
Beamer 2.0 is free to try, and a personal license costs $15. It requires an Apple TV and OS X Mavericks (10.9).
For Merlin Mann's recommendation of Beamer 2.0, check out MacBreak Weekly episode 400.