[Please note. Do not use this guide for pirated materials. This is the only the means, the end of which you decide]
I hope I am not breaking any forum rules by this. This is just a guide. What you do with it is your ethical decision.
You might have noticed that you can't usually add your media files to iTunes library due to a different format. Now the purpose of adding to iTunes could be many.
- Easier access to media while in Front Row
- Better organisation of TV shows/music videos which were not downloaded from Apple iTunes Store.
- Managing your media with movie information, Cover art and such.
- You can play MKV h264 files without the loading time associated with Perian codecs.

Actually, there is nothing to this process. But since I found this tip to be so amazing, I thought I'd share it.

Basically any file that opens in Quicktime, can be converted to work with iTunes. So you open the file, Save As, and save it as a self contained movie. After that you can just add the file to iTunes by dragging it to the Library in the sidebar. Note that if you don't want to copy your media over to where the iTunes library resides, you can deselect the "Copy files to iTunes folder" in the iTunes settings > Advanced tab. Just change it back whenever you are adding music files and such. Also, do not ever click the "Consolidate music library" cause it will copy all your files and going to create a mess.

Alternatively, you can just save the movie as a "Reference movie" and add that reference movie to your iTunes library. This way, your original movie is untouched, the benefits of which are:
- Quicker
- You don't mess with the original container (DTS soundtracks behave differently if in a different container than originally muxed)
- You can transfer the original avi or whatever to a PC and play it there as the .mov container sometimes causes problems on a PC (even on VLC)

Once in iTunes, you can just right click, Get Info, and in the Video Tab, select the video kind as TV show, Music Video, or Movie (default). Of course, you can add cover art by selecting all the files of a particular type, Get Info, and then drag an image into the "Album art" box in the lower right.

There you have it, your media in your Front Row interface, ready to view.