If you have a 3D video in Side by Side format (SBS) this means that the images for the left eye and the right eye are transmitted in the same frame at the same time. If you see a Side by Side video on a normal TV or monitor you will see both images beside (You can try that by downloading a 3D movie (*.mkv) and look it in Zoom Player or VLC Player).
Even on a 3D TV (like the current LG models (in 2012) wich use polarized light) you initially see both images side by side.
Only after switching the TV to 3D mode via remote control the TV will separate the two images one for each eye and they can be seen 3 dimensional with the glasses.
So the answers given above (the 3D signal is a encoding, just like color is an encoding in the signal) are nonsense.
The only thing you need is a TV that allows to switch a side by side video into 3D mode via remote control.
I repeat again: A 3D video is a normal video that shows both images at the same time in the same frame! It is the television that separates them for the eyes, not the computer.
And: It does not matter if the TV uses polarized light or shutter glasses: The video is the same: side by side.
Have a look here: http://www.youtube.com/watch?v=C4x6smktTJQ and you will understand.
P.S: If you have a LG TV you don't even need to connect your computer directly with the TV (no HDMI graphics card required). Instead you connect the TV via network cable with your router and install Nero Media Home on your PC that comes with the TV on a CD. This is a media server that streams your videos and photos into the home network. With the remote control you can chose a movie from that server.