Additions to Format drop-down

Howdy folks, I’m hoping there’s a plugin out there (or a fairly easy method) to add extra options to the ‘Format’ drop-down when writing a Post / Page. All I’d like to be able to do is to select a bunch of text and use the format drop-down to wrap the content in <div> </div> tags. Just that would allow me to hook-up sufficient CSS to allow the page styling that I want.

I might be able to manipulate the <address> tag I suppose, but I’d prefer something semantic and good. It needs to be on a per-post basis as this particular website contains articles with a lot data in them and we’d like to retain the layout style that we’ve had with our static HTML site in the past.