Both Robb Cutler and Chad Clites have the best answer: use pencil and paper.
I am saddened to admit this was not my first answer.
The dominant paradigm of computing education is to teach technology. In the APCS course, are we really teaching the major concepts of computer science? Or are we really teaching Java, and using some of those concepts along the way? It's endemic in the way we talk about our curriculum. We teach "programming with Alice" or "simulations with Flash". If we're teaching simulation-building, why does it matter what tool we use? But we get caught up in the tools, partly because we tend to love them, and the concepts and ideas become, at best, co-equal, and more often subsumed in importance.
The reality is that my current curriculum would not move forward without power. I've faced this problem repeatedly over the last three years and it hasn't been pretty. Last year I spent the first week of school without access to my classroom, having to teach outside. So instead of starting the "real" curriculum (animation with Flash), I did CS Unplugged activities. Sure, I think my students got something out of learning about sorting and searching. But the reality is that the lessons were totally disconnected from the curriculum. The ideas weren't reinforced throughout the year, the concepts weren't connected to anything else they learned, and I suspect that few of them remember anything about it.
We need a new kind of curriculum, that is concept-centered, more like math and science curricula, that sends implicit and explicit messages to the students about what is important, and where what is important is the concepts, not the technology. In the same way that experiments are the implementation of science, but what we teach is scientific thinking and important concepts and knowledge, we need to have programming and computing be the implementation of computer science, but teach computational thinking and important concepts and knowledge. The computer needs to be a tool, not the center of the program.