WorldEdit
sfan5

In-game world editor. Use it to repair griefing, or just create awesome buildings in seconds.

Protector Redo
TenPlus1

Lets players craft special blocks to protect their builds or disable PVP in areas.

WorldEdit Additions
Starbeamrainbowlabs

Extra tools and commands to extend WorldEdit. Currently has over 22 commands!

Playtime Recorder
Lejo

Use /playtime to get the time you played

WorldEdit Maze Generator
wsor4035

A maze generator

Mapserver
BuckarooBanzai

mod for the mapserver

Internet Relay Chat
kaeza

Connect your server to an IRC channel, and install irc_commands to control the server from IRC

Discord-Minetest Relay
archfan7411

Mod + external program providing Discord relaying and commands.

NextGen Bedrock
StarNinjas

Adds an indestructible bedrock layer at the bottom of the world.