Yout - YouTube to Mp3 Converter
y2mate - Y2mate.
Softorino YouTube Converter - Download YouTube video & audio. Watch and listen offline
y2mate.tv - Y2Mate YouTube Converter is not just a video converter, but also an audio converter. You can easily convert YouTube videos to the format you want, such as MP4 (320p, 480p, 720, HD 1080p), 320kbps MP3, M4A, WEBM, etc.
You-Get - Command-line utility to download media contents from the web
Keepv.id - Keepvid is the best online video downloader. Here you can download videos from 100s websites: Youtube, Facebook, Instagram, Twitter, etc.