The multiple-file download is a collection of extensions that use the new download attribute in HTML5 to offer multiple-file downloading. Simple as that.
This is not meant to be a "download accelerator," "download manager" or anything like that. It is meant to work within the browser using the browser's own download capabilities and features. It simply lets a user quickly choose and download the content that is marked as downloadable on the page. This should really be a built-in feature of browsers, since the download attribute is now somewhat standard and defined in HTML5.
The Chrome version is ready for field testing.
The Firefox version is ready for crash testing.
Find features, implementation details, and miscellaneous discussion on the wiki.
Report bugs, request features, and request pulls in issues.