SimilarChannel - Find Similar Youtubers and Channels like your Favorite Channel
Youtube Detox - Distraction-free Youtube search
ViralStat - All-in-one tool for cross-platform social video analytics
YouTube Realtime - The true subscriber count for YouTube, with comparison too.
SimilarChannels - Find similar YouTube channels, discover new channels based on your interests, create your own YouTube collections with your favorite channels.
YouTube Messenger - YouTube in-app video sharing and messaging