Fredboat - FredBoat is one of the best online music bots for Discord.
24/7 Discord Bot - 24/7 is a discord bot that lets you play songs on-demand or listen to a radio station all day long without ever having to stop.
Zandercraft - Zandercraft is an amazing discord bot that includes musical playback and a bunch of other cool features.
Groovy - A dynamic language for the Java platform
ProBot - ProBot is an incredibly cool, customizable bot that lets you design your own bot server.
Hydra - Project planning & management for professional services