I came back from break to an email from an employee at Ginger Software. They have developed a new program for people with Dyslexia and other learning difficulties.
Ginger Spell uses context to correct, with the click of a button, whole sentences containing misused words and multiple severe spelling mistakes.
Click on the post title to connect to www.gingersoftware.com where you can download the free Beta version and try it out. They don't have pricing determined yet so it is free until mid 2009. They estimate it will be about $100 for a home user annual subscription. It's currently for windows only but they are working on a mac version.