If you plan to deploy your client application as an HTTP application then there isn't much you can do other than let your web application handle it (php/python/ruby whateveer).

Another option is writing an uploader as a stand-alone application (such as flickr uploader, facebook's iPhoto plug-in and alike)

The third option is BAD but still exists on facebook as java applet within the browser.

The forth option is to write the client in one (or many) of the browser extenders such as Google Gears, MS Silverlight, Adobe Air/Flex/Flash to do this (look also at http://www.jnext.org and http://www.google.com/search?q=flash+uploader).

All these 3 can be implemented at the server side in whichever language you choose.