There are many native Japanese speakers and writers on JCJP. I believe one of them is the administrator, beeant, who has Facebook and Twitter pages (see the bottom of the login page) or e-mail [email protected]. He is a busy guy, so his replies may take a while.
There are other sites which are specifically made to match you with a native speaker of the language you want to learn, you might find that easier than trying to get someone on here to give up time to teach. Livemocha and... lang8? are two, I believe. My wife is Japanese, if I make a mistake, she'll let me know... -_-