Megawords is a workbook based curriculum that teaches spelling, reading, and usage with word lists arranged by spelling patterns and word structure. It is designed for grades 4-12. Read more about it here.
<b>Comment: </b>This is our first year using this after trying many other spelling programs. All of my kids like it, and my struggling speller is starting to understand spelling. Unlike other programs, this one breaks the words down into syllables to spell, and it gives you rules for the syllables. This has really helped all of my kids to spell words they don't recognize. Just make sure you get the teachers guide to go with the workbook. There are a couple of sections in each chapter where it is needed.
<b>Comment: </b>We are using this currently, I decided to get it for my oldest because he has really bad spelling. I didnt get the teachers manual and I think that makes this curriculum much more tricky to use, I think it would be better if I had gotten it, I have to do a lot of guessing to know what he is supposed to do. But I do like how the book is layed out and I think it is a good way to teach spelling and bigger words.