Hopper
FaceDeer

Adds hoppers to transport items between chests/furnace etc.

Loria (alpha)
siegment

Survival in hardcore acid-alien sci-fi themed world

Ocean
StarNinjas

Adds coral reefs, fish, decorative ocean blocks and much more!

Too Many Stones
JoeEnderman

18 new stone types that all spawn in the world on all mapgens but v6.

Pontoons
FaceDeer

A "floating" block that can be placed at the surface of a body of water without needing to build pilings first.

Timber Frame
jbb

This mod adds timber-framed clay, bricks, cobble, stone and stone bricks to the game.

Morebricks
CalebJ

Adds an assortment of new bricks to build with.

Placeable Buckets for Catching Rainwater
Noodlemire

Allows empty buckets to be placed as nodes in order to collect rainwater.

Castle Gates
FaceDeer

This is a mod all about creating castle gates and dungeons

Castle Lighting
FaceDeer

This mod contains medieval castle lighting solutions

Castle Masonry
FaceDeer

This is a mod all about creating castles and castle dungeons.

Ropes
FaceDeer

Adds rope boxes of various lengths and also rope ladders.

Factory bridges
mt-mods

This mod adds a steel bridges, railings and stairs in Minetest.

Castle Tapestries
FaceDeer

This is a mod for creating medieval tapestries, as found in castles

Castle Shields
FaceDeer

Adds decorative wall shields

Parcdeco
Floatland

adds grass-like nodes that have flowers

Poly Decor
PolySaken

My spin on decorative stuff.

Template to Easily Make Fancy Voxelized Models
Noodlemire

Provides voxelmodel.obj, a model designed to be shaped by changing its texture, in order to easily create fancy voxelized models.

Plastic Box
Starbeamrainbowlabs

Adds a recolourable plastic box. Fork of @cheapie's version with improvements.

You Can't Touch It Either
Avicennia_g

Simple mod adding lockable storage shelves to Nodecore.