Super simple early skyblock mob grinder which will replenish mobs faster than you can kill them (no redstone / plus some upgrades). : r/technicalminecraft
How to Make a Mob Spawner in Minecraft (with Pictures) - wikiHow
Come creare un Mob Spawner in Minecraft | Salvatore Aranzulla
An Exhaustive Guide to Building Mob Traps in Minecraft « Minecraft :: WonderHowTo
Giant Mushroom Mob Generator -- With a couple stacks of dirt and bonemeal, and about 20 minutes, you can build your own high-throughput mob generator [Video in Comments] : r/Minecraft
How to Make a Drown-Style Mob Grinder | Mine, build, eat, repeat ...