JDownloader is a free downloader software. You can use it to download youtube videos and more importantly the whole playlist videos.
I had a need to download the excellent PowerShell tutorials “Learn Windows PowerShell in a Month of Lunches” by Don Jones. Link below:
However, this is a playlist and contains 99 videos. It is tedious to copy each and every video and download through keepvid.com. An excellent online video downloader. To download from JDownloader, copy the youtube playlist link and open JDownloader, click LinkGrabber section in JDownloader. It will automatically detect and select complete Playlist.
If there is any drawback using this tool, it simply creates folder for every video we download and places the file inside the folder. That is a bit annoying.