1. Open http://keepvid.com/
2. Paste link to Youtube clip, e.g. http://www.youtube.com/watch?v=B4GJ0-DR1JM
3. Select "download mp3".
4. It will redirect you to http://snipmp3.com/, where you need to click "download mp3" again.
5. On my machine first click doesn't work, but it works if I repeat it twice.