Protector Redo
TenPlus1

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

Protector Redux
sorcerykid

An efficient and flexible node-based protection scheme for multiplayer worlds

Traders
Sokomine

Configurable mobs/NPC which can trade for you.

TP Gate
AiTechEye

Teleport through the gate

Smart Renting
AiTechEye

Smart renting: Rent out your locked things and earn money!

Global Bulletin Boards
FaceDeer

Allows creation of global bulletin boards where players can post public messages