FameBit - Easiest Way to Find, Hire, and Work with YouTube Influencers
CONV. - Convert YouTube video to MP3, GIF or MP4
inzpire.me - An end-to-end solution for influencer marketing
Downie - Video download for OS X. Downie supports at this moment over 1,000 different sites.
Insense & Paid Media - Find creators for short-term and long-term partnerships
Yout - YouTube to Mp3 Converter