There are various ways of converting YouTube clips to mp4 format so they can be played on portable devices such as Video iPods, iPhones and PSPs. However, the beauty of Tooble is that it can do this for multiple clips automatically and simultaneously making the process so much quicker and easier.
The software can be configured so you can choose exactly what you want to download, be it individual clips, a user's whole channel or the results of a keyword search amongst other options. You can also choose the video size and where to save the clips too. Go to the Options menu and select Preferences for more information.
Once you've downloaded, installed and launched Tooble, you will see a screen like this.
Click the green cross and add the username gorseygorsey. Click OK.
Select gorseygorsey and click Uploads
All the videos from that channel will then appear.
Select the clip(s) you want to download (La météo in this case) and click Download Checked Videos
Your chosen clip(s) will then download as an mp4 file. When complete, click the file to open the clip in iTunes.
From here you can transfer the clip on to your iPod and watch it on the move. Simple
As an alternative to Tooble, have a look at ytpodcaster and Savevid which also allow you to download YouTube clips in iPod friendly mp4 format too. You may wish to create your own RSS feed for Google Reader so you can search for suitable videos by username or keyword. I've found that very useful myself.