Protector Redo
TenPlus1

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

WorldEdit
sfan5

In-game world editor. Use it to repair griefing, or just create awesome buildings in seconds.

WorldEdit Additions
Starbeamrainbowlabs

Extra tools and commands to extend WorldEdit. Currently has over 22 commands!

Internet Relay Chat
kaeza

Connect your server to an IRC channel, and install irc_commands to control the server from IRC

Mapserver
BuckarooBanzai

mod for the mapserver