Fine Uploader
Multiple file upload plugin with image previews, drag and drop, etc.
... and notify the user, or even automatically retry uploading the failed piece. Pause an in-progress upload when you know you are about to go offline, and safely resume them again right where you left off. Splitting a file into smaller pieces allows for a more efficient overall upload, and powers some Fine Uploader features such as pausing, and resuming uploads. Fine Uploader can also upload multiple chunks for the same file concurrently.