I don't know much about online journals, since I just buy a notebook and write everything down by hand.
It's a great way to express how you're feeling and get it off your chest. I have four, filled cover to cover, from as far back as six years ago. I have great difficulties discussing my problems in person, but give me a chance to write it down, either on paper or online, and the flood gates open.

I don't know where I'd be without my journals. Trust me rtrudeau, it helps.