Most people, whether native English speakers or not, could do with some help with their spelling. Speak N Spell is a program that will do just that, and is suitable for adults and older children alike.
Small, compact Speak N Spell is designed to help people practice their English spelling, a helpful goal given the language's notoriously difficult, non-phonetic words. It works like this - you pick the level of difficulty (1-5) and click "new word". Speak N Spell then reads a word to you and you type the correct spelling into the box. If you get it correct, you ask for a new word; if not, you have two further chances. You can ask Speak N Spell to say the word as many times as you like, ask it to display the correct answer, or pass.
Speak N Spell uses a pre-programmed list of American English words - over 47,000 of them. You can modify this list or even add your own, deleting and adding terms as you like. All of the basic functions can be controlled with hotkeys, and the program remembers your preferences even after shutting down.
The voice that you hear is whatever voice you have activated in the Control Panel > Speech > Voice Selection option. The author of Speak N Spell recommends Vicki and a slow speaking voice, and from my own experiments, some voices are definitely more intelligible than others. Experiment until you find one you like.
Speak N Spell is a simple program that does exactly what it says it will - help you to improve your spelling.