Industrious by StarNinjas
Adds new industrious-themed blocks and tools.
Buszmo's building gallery
A collection by Buszmo
Packages
X-Decor-libre by Wuzzy
A decoration mod meant to be simple and well-featured (libre version).
Blox by mt-mods
Adds lots of differently colored and textured blocks to Minetest.
Placement Preview by SURV
shows a preview with orientation of the node the player is holding.
WorldEdit by sfan5
In-game world editor. Use it to repair griefing, or just create awesome buildings in seconds.