Great Downloader easy to use can convert into multiple file formats. Fast and impressive
LameXP - LameXP is an Audio Encoder Front-End, a graphical user-interface for a number of audio encoders.
Video DownloadHelper - Browser extension to download videos from the Web
SoundConverter - The sound conversion application for the GNOME environment.
youtube-dl-gui - A cross platform front-end GUI of the popular youtube-dl written in wxPython.
fre:ac - fre:ac is a audio converter and CD extractor designed for Microsoft Windows, Mac OS and Linux, distributed under the GNU General Public License.
Youtube Video and Audio Downloader - Download YouTube videos in all available formats and extract the original audio files.