I wanted to view youtube videos on my phone, but unfortunately the mobile youtube site seems to have less content than the full site. So I decided to make my own mobile phone compatible video files and upload it to my phone. First things first I needed to get the flash video file from the youtube URL, which can be done with this handy site. Next i needed to convert the flash video into a .3gp file that is compatible with my mobile phone. This can be done using ffmpeg (I used a windows version of ffmpeg)
I converted the flash video using the following command.
ffmpeg -i movie.flv -s qcif -r 12 -b 30k -ar 8000 -ac 1 -ab 12.2k movie.3gp
Finally I copied the files into the video folder on my phone using standard USB Storage Media drivers in windows, which simply present my phone to me as if it were a Hard Drive.
Giles Bathgate 
The “Fast Video Download” Firefox plugin is good for grabbing YouTube videos (and lots of other things) straight from the browser.
I read your blog in a regular manner and just love it
hope there will be more postings from you, keep on going
greetz, carmella
This is just priceless:)