How could we create an add_meta_box field that supports image upload over ajax

I am using WordPress 3.0 and have multiple custom post types set up.

My custom post types have custom meta data fields associated with them using add_meta_box.

I would like to be able to add a meta box that would allow you to select and upload an image, which is then uploaded and attached to the post over AJAX. The path to the attached images would then be stored as the value of the meta box and the image displayed on the write panel.

Ideally some resizing of the uploading images would be allowed.

I would like to hear how this could be done, without plug-ins.