HTML 5 work includes a multiple selection option for <input type="file">:
http://www.whatwg.org/specs/web-apps/current-work/multipage/forms.html#attr-input-multiple
This is now supported in WebKit development trunk:
http://trac.webkit.org/changeset/37863
Using this in the UI when Flash or other fancy upload controls aren't available would be a nice assist for supporting browsers.
(Requires actual support for handling multiple file uploads -- bug 16751)
Version: unspecified
Severity: enhancement
URL: http://commons.wikimedia.org/wiki/Special:Upload