• Use hidden iFrame for IE < 10
  
• Use Flash for older versions of browsers
  
• Use XMLHttpRequest for newer browsers
  

• Use Flash
  
• Use canvas + blob
  

• Dropzonejs - IE10+ 
• Blueimp jQuery File Upload (all browsers)
• jQuery Form Plugin (limited, good for older browsers)
• Plupload (all browsers)
• FileAPI and it's jQuery wrapper jQuery FileAPI (all browsers)

• Supports HTML 5 features
  
• Falls back on Flash for older browsers
  
• Superb image processing capabilities
• Has jQuery plugin (wrapper)
• Totally free with no strings attached

• CSRF token
  
• MIME validation
  
• File names
• Protect Uploads folder and temp folder
  
• Delete temp files (cron job)

1. Upload to temp folder + return file name back as JSON
   
2. File name is stored in hidden input field
3. On form submission move the file to 
   permanent location if validation passes
4. Run a cron job to clean up temp folder every X minutes

 $now = time();
 foreach(File::directories('public/uploads/temp') as $dir ){
    $dirtime = filemtime($dir);
            
    if( $now-$dirtime > 3600){
      File::deleteDirectory($dir);
      $this->info('Directory '.$dir.' was deleted');
    }
}

• Dropzone.js example
• jQuery FileAPI example from Laravel-tricks
• Upcoming chapter of  my Frontend Book