MCManager - The ultimate Minecraft content manager.
Install mods, texture packs, save files, and jar files to your minecraft folder, and automatically do anything else you'd otherwise need to navigate to .minecraft to do.
An alternative/custom Minecraft server, written in Java, compatible with the original protocol. OpenCraft is built upon Apache MINA, SLF4J, Jython and XStream. The aim is to have features not in the official server distribution, like antigrief/scripting.
Opticraft is a custom server for Classic Minecraft multiplayer developed in python. It makes use of no extra dependencies, it is not based off Myne, and requires python 2.6. It aims to be light weight as well as easy to setup and use.