Today you can get two applications which can help you to download video and audio from the YouTube.
Abelssoft YouTube Song Downloader 2014 is the application (free version) I am using when I want to download video or audio from YouTube . It is simple to operate and any user can easilty download. You can either search for videos directly from the application or can copy paste the url of the YouTube video to find the video you wanted to download.
You choose video or just the sound track from it
You can get this application from Glarysoft for free ($10 otherwise). The offer is valid just today - http://giveaway.glarysoft.com/youtubesongdownloader2014%28build10.2%29-849/###.
Airy YouTube Downloader which costs $19.95 is also free just today via Giveawayoftheday. http://www.giveawayoftheday.com/airy-1-0/.
Download in different formats. MP4, WebM, FLV, and 3GP
Supports different resolutions
Extract the audio as Mp3
Airy bookmark to add a url directly from browser to the application
Use the code from the file you downloaded to activate the application
Both the applications are good, so you may grab one of them (or both) if you wanted to store the videos to your hard disc and watch it offline.