all "ajaxy" looking solutions use an swf object to do the upload job. you can home-cook your progressbar if you have an op-code cacher like APC
Here is Martin Jansen blogging about Rasmus Lerdorf's simple upload code which in the end uses APC
http://martinjansen.com/2007/04/28/file-upload-progress-bars-with-php/
and a working example