Bukkit

Commandless, Multi World, Player Owned Shops (Vault)

Who wants long wires? Go wireless!

Allow players to get and craft items of power

BetterAlias

Allow players to buy&sell from a single global shop

Disguise yourself as a block!

Let your players hunt epic level bosses and craft powerful items from their remains.

Change the amount of feeding/healing individual foods give!

Send fake (+colored) messages to players!

A simple points-based reputation system