Yout lets you convert and download YouTube videos to mp3 (audio), mp4 (video) or gif (image). Works for Facebook, Vimeo, Twitch, Twitter, VK, YT, Instagram, SoundCloud music and many more sites with Yout, the DVR (Digital Video Recorder)
SYC 2 is a $20 Mac & Windows application from Softorino, the folks behind the insanely useful and clever WALTR software. Like that software, SYC 2 makes it easy to sync videos/audio from online sources directly to an iOS device without the need to first import them into iTunes.
YTBmp3 is an app for converting YouTube videos into mp3s.