I'm considering using SWFUpload on my site, but I saw that the last release was in March 2010, and it was a beta. It looks like the SWFUpload people stopped there development.
Is this project still alive? Is there an alternative?
In my opinion, SWFUpload looks pretty dead...
No Issue updates since June 2010 at Google Code...
http://code.google.com/p/swfupload/issues/list
There IS lots of recent activity at the official SWFUpload discussion forum. Have you asked there yet?
http://groups.google.com/group/swfupload/topics
As far as alternatives, there's quite a few...
http://www.solmetra.com/en/disp.php/en_products/flash_uploader/uploader_intro
http://www.codeproject.com/KB/aspnet/FlashUpload.aspx
EDIT:
http://digitarald.de/project/fancyupload/
This article contains a few already rejected outright by OP, but the others are worth looking...
http://www.cult-f.net/multiple-file-uploaders/
http://valums.com/ajax-upload/
http://clubajax.org/the-new-dojo-html5-multi-file-uploader/
EDIT 2:
How can I upload files asynchronously?
http://www.freshdesignweb.com/10example-ajax-upload-file-with-php.html