Sometimes I have trouble picking the right words to use when I write an English phrase, i.e., I mix tenses, double negate some expressions and so on.
One thing that helps me write better English and improve my own knowledge is by learning from my own mistakes using software like StyleWriter, but since it's quite old and we are in the Web 2.0 era, I'd like to know if there is any online service / tool that I can use to achieve the same effect.