Aternos - With Aternos, you can run your own Minecraft server for free.
Server.pro - Free and premium game servers for Minecraft, Terraria and Hytale
Spigot - Simply put, Spigot is it.
Minehut - Free Minecraft server hosting
Glowstone - A fast, customizable and compatible open source Minecraft server.
PloudOS - Why buy a server if you can get one for free? Get your own Minecraft Server for free today!