I have a spell checker for most of my posts. She sits in her room reads my posts then tells me all the spelling mistakes. She also doubles as a grammer checker.
I'm practising writing as the French speak, no commas and full stops only when really necessary and then in the middle of a sentence. - (deep breath smiley)
If you load a spell checker into your browser you can spell check while you type.
There are free spell checkers for internet explorer and firefox which work pretty well, they're not perfect but they're adequate. Here's an internet explorer one and here's a firefox one