I recommend three software for youtube video download, and they are flashgot (firefox plugin), youtube-dl and uget.
I call these software hidden gems, because one complements others. Typical use case of these software is to download tutorials, videos for offline view etc.
First, you have to install them using the usual procedure (flashgot using firefox addons, uget and youtube-dl using software repository of your distribution). Here is the command to install uget and youtube-dl on Ubuntu.
$ sudo apt-get install uget youtube-dl
Note: If you want to get newer features of uget, better consider installing it from the official site.
In case of youtube-dl you also have to update it via the command line after the installation using
$ sudo youtube-dl -U
Depending upon the message given by above command, you might have to run the command couple of times to get the latest update.
After you install flashgot in firefox and restart it, go to Addons->Flashgot->Preferences->FlashGot Media and select Uget from the dropdown menu and click Ok. This should set Uget as the media downloader for flashgot. Also set it in General tab.
Youtube-dl comes handy when you have a list of files to download. Create a text file with links of youtube videos you want to download (one for each line, without additional strings).
E.g One example would be
https://www.youtube1.com/watch?v=abcdva129 https://www.youtube1.com/watch?v=abcdva128 # and so on ...
To download all these videos you just have to run following command in a terminal
$ youtube-dl -a ourlist.txt
Great thing about having a command line tool is, you can mix it with multiple commands. E.g write a script that executes above command first and then shutdown command next to turn off the computer. This way you can schedule the download at night.
# myscript.sh $ sudo su # youtube-dl -a ourlist.txt && poweroff (be aware, you are running it as root)
2. Uget with Flashgot
While browsing via firefox, if you happen to like some videos, just start playing it, an icon should flash on top right corner (if not, use the customize menu and drag it there). If you right click this icon, it should show all the options (video formats and sizes) available for this particular video. If you click on one link from this list, uget should start downloading the video.
Uget lets you set size of a queue (right click the section under Category and go to properties and set Active downloads to the number you prefer for queue).
If the video download cookie gets expired (e.g you turn off your computer for long time), you can go to the download page of the incomplete download (using links from properties) and obtain new cookie for that file, which you can set in properties to resume the download. If that does not work, you can download new file (set previous video format, size and name) to resume the download.
I hope you have found this post helpful, if you were not aware of these software before.