Recently, I wrote about "using free software to turn/rotate/flip video movie" which can be done with 2 Windows based applications namely Windows Movie Maker and Free Video Flip and Rotate.
Now I am going to write about Avidemux, which can do the same video rotating function, and is multi-platform (can run in Linux/BSD/Solaris/Mac/Windows). Being GNU GPL licensed, you can also install and use Avidemux for free.
To rotate a video, open the video file. Then, change "Copy" in the Video section to one of the video format of your choice.
After that, click on the "Filters" button.
Double click the "Rotate" option under the Transform filter, and select the rotation degree. You can click the "Preview" button to see how it is going to look like.
Close the Video Filter Manager when you are done. Save the video with a new filename and you will get the rotated video.
Click here to go to the website of Avidemux.
If you are using Ubuntu Linux, you can probably install Avidemux with Synaptic Package Manager.