I have Firefox as my browser and it does such a good job of spell checking that my spelling gets worse by the day. I get lazier and lazier, knowing that Firefox has my back on spelling, @Cruiser.
There are Fluther members that are ‘given a pass’ because their English usage is so consistently poor, @cheebdragon. Even questions are not held to standard English.
For these reasons, I would have to give @Dan_Lyons book serious consideration.
Personally I learned my vocabulary by reading, and I was more interested in the story than the mechanics, and my spelling has always been borderline. If you’re still doing a lot of longhand writing, you might still be in school, and if you’re still taking classes there might be tutorial help available. Ironically, I once tutored a Senior in college on spelling (I was soph.), but I don’t remember what success we had, if any.