1.We can't download videos from YouTube.com directly.

So we use third-party site or tool to download YouTube videos
There is a easy to use and free Video Downloader on topsevenreviews. Free Video Downloader can download videos from YouTube ,Google ,My Space .

http://www.topsevenreviews.com/free-...ownloader.html

Video Downloader is a completly free Software.Video Downloader is very simple, so you don't need any technical knowledge to use it.

Just as follow steps.
(1) Run Video Downloader and start downloading!
(2) Paste URL of movie and press Start button.

2.Convert YouTube ,Google ,My Space video to iPod/Zune/iPhone/PSP

(1) Choose a video converter by reading the popular video converter reviews .
The videos downloaded from YouTube is FLV formats, and google is GVI,AVI,or MPEG4 formats .
So, if you want to play videos downloaded from YouTube ,Google ,My Space to your iPod, Zune, iPhone, PSP ,cellphone and other portable players.
You Should convert the downloaded video files to iPod, Zune, iPhone, PSP etc.supported formats .

See the reviews about all popular video converter reviews.

(2) Use Video Converter or FLV video converter to convert videos to WMV,MP4,AVI etc.

Step by Step convert video to iPod, Zune, iPhone, PSP ,cellphone and other portable players.

Step 1: Download Video Converter or FlV video converter, and install it .
Step2: Add video file to Video Converter or FlV video converter.
Step3:Select the videos you want to convert.
Step4: Select the output iPod Video format by choosing from output profile combo-box.
Step5: Custom output files by adjust some settings, Or you can just keep the default settings.
Step6: Convert .

I googled Wondershare YouTube Downloader not long ago. It is very practical and convenient to use.
It is a powerful tool to download youtube video from the Internet and convert youtube flv video off the Internet.