Flickr has just announced that they are now supporting Internet Explorer 9 with their new HTML5 based Uploadr.
The company said:
We just added IE9 support to the New Web Uploadr. You can bask in all its glory right away, but in case you encounter any issues, this thread is for you. Please note that certain browsers do not support all the HTML5 features that the New Web Uploadr offers. Since IE9 is one of them, a small set of features like preview thumbnails for your photos or drag & drop will work delayed or are not available if you are using IE9.
If you are going to use Flickr Uploadr using Internet Explorer 9, keep an eye on this thread.