Downloader/converter for youtube to MP3 player

[a-10tankkiller]

I bought one of my sons the Sandisk Sansa Fuze and his oldest brother wants to put videos from youtube and probably elsewhere on it. He says we need to download a converter(file converter I'm guessing)to be able to get the computers to the MP3 player. He has some ideas friends gave him, but I thought I'd check here for ideas if anyone has some and I'v made any sense about what I'm looking for.
On a side note, anyone see the NFL ads for fantasy football? Those are what gave the oldest the idea to download videos for the MP3 player.

[mcs328]

media converter for filefox. it's a plug-in and it works really well.