Pop up post submission form

Morning all,

On my site i would like the option for people to submit their own posts, effectively creating a blog that is by friends. I know this kind of falls under a forum but in keeping with my site I would call it a blog.
I would like a link that when you click it, a pop up appears with a form to fill out (their post) and then when they submit it, it comes in for moderation.
Is something like this possible? Is there a plug in out there for this already?

Many thanks in advance all.

James