good news, Yahoo Maps has published an API in pure AS3! This is great news. Click here. The past answer was using the AS2 component with an AS3 wrapper, it didn’t appeal to me at all.
Here is a tutorial on how to use their new API inside of Flash CS3, cause apparently it’s mostly Flex oriented (like most things eh?).
Following this link you will find a blog entry on a little app the guys inside of Yahoo built. Somebody should tell them about the ‘smoothing’ property of Bitmap object in AS3, it would make the rotated maps look much better!