UTube Ripper is an application written in Gambas, that works exclusively on Linux. With this free application, you can download YouTube videos in a simple and efficient way.
Using UTube Ripper, you can also convert YouTube videos, which are in flash format, to a non-flash format. Using the “Rip audio only” option within this application, you can extract audio from a YouTube video, and then convert it into MP3 format.
You can download the .deb package (debian package for Ubuntu) for UTube Ripper from here.