Fine Uploader is a multiple file upload plugin with image previews, drag and drop, progress bars. S3 and Azure support, image scaling, form support, chunking, resume, pause, and tons of other features.
Upload Preview jQuery plugin provides an easy way to preview your uploads before they're actually uploaded to the server.
So if you selected an image or audio file from your hard drive, it will generate a live preview of the selected image or audio player for the audio file.
It has a plugin-based architecture, first-class support for resumable uploads according to the open standard: tus, and custom encoding backends, making it extensible and robust.
jQuery.filer is a simple HTML5 File Uploader, a plugin tool for jQuery which change completely File Input and make it with multiple file selection, drag&drop support, different validations, thumbnails, icons, instant upload, print-screen upload and many other features and options.
Dropper is a jQuery plugin for simple drag and drop uploads.
JSAjaxFileUploader is a jQuery Plugin with ease of use. Fully customizable with many options. You can have multiple upload forms in a same web page at the same time and user can also select multiple files for upload.
jQuery Upload File plugin provides multiple file uploads with progress bar.Works with any server-side platform (Google App Engine, PHP, Python, Ruby on Rails, Java, etc.) that supports standard HTML form file uploads.
Nice tutorial about creating an AJAX file upload form, that will let visitors upload files from their browsers with drag/drop or by selecting them individually.