Great Downloader easy to use can convert into multiple file formats. Fast and impressive
Video DownloadHelper - Browser extension to download videos from the Web
Openwhyd - Collect and Share the tracks you love.
youtube-dl-gui - A cross platform front-end GUI of the popular youtube-dl written in wxPython.
Music Smasher - Find any song. Music Smasher searches Spotify, Rdio, SoundCloud, Bandcamp, and YouTube.
Youtube Video and Audio Downloader - Download YouTube videos in all available formats and extract the original audio files.
FoxTube - Play YouTube video continuously with playlists. FoxTube features: