What are some good examples of educational software?

I have seen people promoting programs that lead students step by step through lessons, asking questions and adjusting the lessons according to whether the answers are correct. This is not my idea of good educational software. To me, a good educational program is one that allows students to explore on their own.

The only such program with which I am familiar is a geometry program called Geometer’s Sketchpad. I am not in the habit of promoting commercial products, but this program is really good, far better than similar public domain programs I have used. It has a very intuitive interface that makes it really easy to create geometric constructions. You can build your own tools and it has an interesting way of generating fractals, all of this without writing a single line of code. It is a kind of visual programming language.

I have heard about animal dissection simulation programs. That seems like a good idea for biology class. I wonder if it would be useful to train surgeons with such a program.

There are programs that do historical and economic simulations. I do not know much about them, but they seem to be a good idea to bring life to these areas. Even better would be programs that allow users to create their own simulations.

From what I have read of Rosetta Stone, I am not terribly impressed. I am expecting dramatic changes in language learning software, making use of what we know about language and artificial intelligence. Consider, for example, the ability of IBM’s Watson computer to interpert questions and answer in intelligible sentences.

Sorry for the length of the question. I easily get carried away on this topic. What other programs do you know of or new ones that you would suggest?