Heavily CSS-based uploader, as seen in Behance's project editor. Only the JS sets the width of the progress bar depending on (of course) the progress. The animation stops once the file is done uploading.
The .file-progress-bar div could easily be changed to a pseudo-element once WebKit supports animations on them. (Firefox already supports this, but I changed the markup for this example. The animation is very pretty and I didn't want it to be missed!)