In iTunes, there are two ways to categorize your videos: as either Movies or TV Shows. I use the Movies category for very large files, and put everything else in TV Shows, because in the TV Shows library, iTunes allows you to create groups. I've created groups called You Tube Videos, Home Videos, Work Stuff, etc.
To create a group, first make sure both TV Shows and Movies are visible in the iTunes source list. If they're not, go to iTunes' General preferences and check Movies and TV Shows in the Show section.
Next, import your new movie into iTunes by dragging it to the source list where these libraries display. In most cases, iTunes will categorize it as a movie. Select the movie and press Command-I to display the Info window. Click on the Options tab, then, under Media Kind, choose TV Show. If it's as short video, you might want to uncheck Remember Playback Position, because you will most likely always want to start these types of files from the beginning.
Next, click on the Sorting tab. Correct the tag that iTunes applied, if necessary, in the Name field. To create a nested group, you must enter some text in the Show field. You'll want to apply the same name for every item in the group, so the files stay in that group. Click on OK, and this will be applied.
When you look at your TV Shows library now, you'll see that all members of a group will display, in Icon or Cover Flow view, behind a single icon. In Album List view, all of the videos will display, but you'll see them sorted by "Show," or the group name you gave them.
[kirkmc adds: This is a good workraound that can help you organize a big video library, though there are some problems. iTunes seems to choose arbitrarily which icon to display when in icon view, rather than, say, the first item.
Another way you could do this, if you want to display the items in Icon view, is to choose to display them by Genre, and apply custom genres to your video files. However, using the Show tag allows this organization to also display on an Apple TV.]
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http://hints.macworld.com/article.php?story=20120310181018710