Great uploader like uploadify but with a "no-flash" fallback [closed]
http://www.plupload.com/ falls back from HTML5 to Flash, Gears, Silverlight and iFrame. It's developed for TinyMCE, so it's extensively tested and actively developed. One downside could be the size, but simply include it only on the sites that need to upload files and reduce size but excluding Gear or Silverlight support.
I am the author of FancyUpload, so believe me when I approve another uploader ;)
Sebastian Tschan just released a great plugin called jQuery File Upload that will likely suit your needs.