Youtube Batch Downloader is designed for all those video junkies that prefer downloading Youtube videos to watching them online. There are other tools to download videos from the popular website, that's true: but this one is special for a few reasons.

First, it enables you to download not only single videos, but also multiple videos at the same time. You can actually download all the videos grouped under the same author, channel or group with a single click.

Second, the program can save videos in a variety of formats, namely AVI, WMV, MOV, MP4 and special formats for iPod and Zune. No conversion process, no waiting time.
The video is downloaded, converted and saved, all in one!
Finally, you can join these downloaded videos into one single file, so that they're easier to watch, especially if they are similar in topic.

The only downside to Youtube Batch Downloader is that you'll probably need to check the documentation if you want to learn how to use, because it's not as easy as it seems.
In any case, documentation is a Youtube video itself, so it's not that hard.
A Youtube video downloading tool that also converts formats and join several clips in one.