M68 is a neat little hostel in East Berlin within walking distance from Checkpoint Charlie. It is relatively cheap and clean. I stayed in a single room and the bathroom was just down the hall. It was almost always vacant, so no problems there. It also has a small cafe at the entrance where they sell some snacks, coffee, and really cheap beer. If the weather is nice, they even put a few tables outside which allows you to enjoy the rare Berlin sun. I recommend this hotel.