If you know any bukkit plugins that are good post them here leave comments!
If you know any client mods or single player mods post them here leave comments...
===List of Mods===
SinglePlayerCommands - Useful in-game commands
Worldedit - Easy quick building
TooManyItems - Single player and Multiplayer in-game inventory editor
===List of Bukkit Plugins===
Showcase - Stone Slab based Shops (Another glass based shop version)
LWC - Easy grief protection lock doors and chests
Alerter - Lock chests doors furnaces more and then set building permissions for certain areas
Bigbrother - Griefer Log
Iconomy- Buy items from shops (Need a shop plugin) using this economy
Jobs- A way to earn money easier on iconomy
Chestshops- Easier Shop plugin needs iconomy though
AdminChat- Chat that admins can only use or whoever you set permissions to
Essentials- over 25+ Pages in-game of commands
iQuests- Get paid for Killing certain mobs and amounts and having certain items
[More plugins to be added - Suggest some in comments]