For SOME modern browsers, you can use the built-in File API. You might find some plugins, but you may find the API does what you need, as-is. MOST of the current browsers support it, with one glaring exception: Chrome on Android. Mobile Safari/iOS supports it from iOS 6.
It's not possible with other browsers. The file-selection dialog is part of the browser, and ONLY allows the user to select files for upload only.
You could play tricks with uploading, and then re-downloading with Ajax. Yuck!
Google is your friend. As well, you will probably get more response about plugins by posting to the Plugins forum section!
Maybe Jake can weight-in - he's done some considerable fiddling with the File API.