Unstable Caves
M BLOC

Some stones may cave in if punched, making underground expeditions more risky.

Fragments
Amaz

A mapgen with a goal, with things needed to advance to the next level.

Nyancat's heaven (reworked)
Hybrid Dog

Adds a nyanland in the sky

Noriel Sylvire's Minerals Core Modpack
Noriel_Sylvire

An API for automatically registering recipes, nodes and ore generation.

World Borders
argyle

Add impenetrable barriers to the sides and bottom of the world.

Boulders
Neuromancer

Adds pushable boulders which spawn in dirt & stone. They tumble when they wind up on top of each other and cause damage when they fall on you.

Purple ore
X-DE

Adds new purple ore to floating islands and caves from height 200 to 31000.

Fix floating sands!
1F616EMO

Avoid hanging sands and gravels

morebiomes
mzs.112000

A simple mod adding a few biomes to Minetest Game

Easter Eggs / Ostereier
Ineva

Adds various coloured eggs for Easter!

Boulder Dig
Neuromancer

Creates gameplay for the game Boulder Dig (inspired by Boulder Dash). Find the boulders and gems scattered throughout the regularly generated world. 2nd option is more densely packed levels.

Sticks Stones
MikeRedwood

Makes Sticks from leaves and scatters small stones

Underground Survival Lighting
Arkatron

If you like underground light in survival, use this mod, it can help that.

golden lava
GigaByte

add golden lava

Startest
Robot10&Scheletor

This mod adds several space stuff to the game.

Tac Nayn
GreenXenith

Adds Nyan Cat's evil twin, Tac Nayn (and a gray-scale rainbow).

Sun Flowers
Hybrid Dog

This mod generates flowers which close their heads at night.

Spawn redo
cathaya7d4

Drop-in replacement for default/spawn for more third-party biomes

Obdy
Sires

Adds some pretty OP tools :)

Fly-B-Gone!
Hugues Ross

Hides butterflies/fireflies

treasures
ademant

Treasure nodes with useful items

Aotearoa
Eris

Fork of aotearoa by Dokimi. Complements the default map biomes with Aotearoa, land of the long white cloud, New Zealand.

Warning: Non-free media.

Mud
Blocky Player

Adds stylish mud blocks and even blocks you can walk through. Setup traps, secret rooms and much more!

Silver
Jackknife

adds silver ore and tools

Too many ores
TeufloV

This adds 53 new ores. But most of them are useless.