Minecraft Single Player (playable without account)

This is minecraft launcher that allows you to play in single player mode without having a premium account. As far as I know, it only updates to Minecraft 1.5.2, but that's better than nothing.

When you launch the game, you don't need to enter anything in the username text box. Just click "Enter Game"
The first time you play it, you may have to wait for it to install the game on your computer.