Remember the movie Gravity? I hope you saw it in IMAX 3D.
If you did then you really got a sense of floating in space. You almost wanted to help the characters grab things!
Now you can experience "Gravity" with the Oculus Rift. The Blue Marble Oculus demo is the closest experience I have found so far. The demo puts you in a space suit floating away from the earth (rather fast).
The effect is pretty fun. There is no movement required, just your head to look around.
You can even play your own music (it has some defaults) for your a journey into space. Just place your favorite songs in the "YourMusicHere"-folder in the Blue Marble directory and select one of them in the in-game menu.
NOTE: Songs must be in the .ogg file format (Due to licensing issues)
In the download there is a program called Audacity with which you can easily convert your mp3's to the .ogg format.
To convert your song, open the mp3 in Audacity > Export > Select .ogg extension > Save.
NOTE: This demo is currently only available for the Oculus Rift DK1