Perhaps I'm a nerd, or I've been out of school for too many years. I found the below link which has a quite comprehensive list of different words which are often mixed up in the English language. If you're needing a review or looking to educate yourself, hope this link helps.

http://www.wsu.edu/~brian s/errors//errors.html#err ors

Hey man that site is just what I needed. I have been spelling medical terms for so long, I usually forget how to spell the everyday ones. Good lookin out!