Partial blog export

A category on one of my blogs has grown to the point where breaking it into an entirely separate blog seems necessary.

Is there a way to export all of the posts and comments belonging to a taxonomy category into a WXR file, to be imported into another WordPress instance? A search of Google has found nothing.

I could probably put together an SQL query that would return all the posts and comments (assuming post_title is used to link comments to posts, not something in the postmeta table; as that would hurt my head too much), but that still means I have to migrate media manually.

So basically, what’s the easiest way?