Are you after a server-side script that will convert the uploaded images to thumbnails, or are you wanting to create the thumbnails locally and then upload them? For a free PHP script you can check out http://www.zubrag.com/scripts/website-thumbnail-generator.php For locally generated thumbnails, use GIMP or Ifranview. Ifranview is probably the right choice for you as it is simple to use and can batch process all your files in one shot.
I ahve used this one a lot and find it to do ma fine job plus its free which is always nice http://www.fookes.com/ezthumbs/
You might check the imagemagick suite of utilities. You may see an example of how I used it to create thumbnails for one of my demos, making images from the command line. cheers, gary
You may find it easier to use a web-based website thumbnail generator like ShrinkTheWeb at http://www.shrinktheweb.com. Service is free for 99% of users and you'll probably enjoy the simple copy/paste of 1 line of code and the optional mouseover preview bubble widget. Cheers, Brandon
Im doing a test of my own thumbnail generator which you may find at: http://thumbdrop.eu Easy & quick TS