Mineshafter Squared is an authentication and texture proxy for Minecraft . It gets in the middle of the game clients and its outbound calls to the minecraft servers. This allows my service to provide its own login system for the game which enables players to try out the game before buying. My authentication service is also online whenever the official Minecraft server's go down. That is not as much a problem anymore, but was very useful in the past.
The proxy also allows me to offer an amazing texture management system that far outshines the official service. Users can upload multiple textures to switch between, discover new textures, and share them with their friends and the community.