If the client machine supports flash,  Ajax Uploader will use flash solution.

 

If the client machine doesn't support flash or silverlight, the select multiple files feature will not be avaialble. However the muliple file upload function will work.

 

Demo:

 

Uploading multiple files like GMail
Google's GMail has a nice way of allowing you to upload multiple files. Rather than showing you 10 file upload boxes at once, the user attaches a file, you can click a button to add another attachment.