The W3C silently published a new draft last week. File Upload specifies an API to upload one or more files from the client. It is intended to add XMLHttpRequest integration as well.
A much needed standard as the current file select control in the input element requires some hacking to produce a useable solution for clients to upload more than one file. Also the limitation of selecting one file per file select control is annoying. I also hope the File Upload standard will include support upload of folders (and sub-folders). Imagine a one-click upload of your entire photo collection to Flickr. Without installing software or using active-x.