Plupload

At its core Plupload is visually flat and you can customize it however you like. We are using HTML5 APIs. Always. Plupload is based on multi-runtime pollyfills for XMLHttpRequest L2, File and Image APIs. So when there's no HTML5 available in the browser, we emulate it ourselves. Files not only can be picked from browse dialog, but also can be dropped directly from the desktop. In some browsers, mostly in those based on WebKit, it is possible to drag and drop whole folders. Since we emulate as much of HTML5 as possible, we are able (among other things) to provide access to raw file data, even in such environments that do not normally support it. One of the biggest benefits of this is that we can display the thumbnails instantly, right as you select the images in the dialog or drag&drop them from the desktop. We slice the files in chunks and send them out one by one. You can then safely collect them on the server and combine into original file.