Recently I've been editing a lot of technical articles. Poor grammar and the use of passive voice has apparently been a bit of an issue for me!
In the course of understanding the difference between active and passive voice, I stumbled over HyperGrammar, which is an electronic grammar course at the University of Ottawa's Writing Centre. It's an excellent website, one which I'm interested in reading - especially as the Australian school system never taught me grammar as it fell out of fashion with the teaching profession. A terrible mistake we are now all paying for - I understand that grammar is now back in fashion, so I suppose that there is still hope.
I just started reading about what a pronoun is, but as it's almost 11PM, I decided to stop when I discovered you can use subjective personal pronouns, objective personal pronouns, possessive person pronouns, demonstrative pronouns, interrogative pronouns, relative pronouns, indefinite pronouns, relative pronouns and, finally, intensive pronouns!