> Is there some tool for downloading video/audio files from YouTube?

If you want to try something different, give Democracy a try.

http://www.getdemocracy.com/

I packaged it and it is available here (the rpm from the official site was broke last time I tried it).

http://people.atrpms.net/~pcavalcanti/rpms/Democracy-0.9.2.2-3.fc6.lcg.i386.rpm

There is also a version available for FC5, but it needs mozilla to run.
I was not able to make it work with Seamonkey yet.

--
Paulo Roma Cavalcanti
LCG - UFRJ