Microblog style posting box

Hi there,

I’m trying to create a microblogging site. I’ve got my layout in a way that I like, but I would like to add a twitter style quick post box, as is present in the P2 theme. One issue is that I need to retain the abililty for users to select a category (in fact it must be essential), preferably from a drop down box below the post box.

Is it possible to just add a box like that to the top of my current theme? If so how is it done? As things stand users have to go through the wordpress backend which I would like to avoid!

Any help much appreciated!

Mike