This is a good and well written site on building basic electronic motors. He has four basic electronic motors, including a hall effect motor. He is selling kits, which look very clean, and well put together, but doesn't pull any punches on his instructions, and as far as I can see, he gives you all you need to gather all the materials yourself. He also offers the harder to find parts individually. What is even better is the author, Stan Pozmantir developed these instructions and kits over a period of three years in high school. He has an easy writing style, and a clear website. Check it out.