So you want a bunch of photos to be resized all in once? Well then bridge is the way to go since it will save you alot of time following the steps below in this tutorial, good luck. Oh and keeping in mind that adobe bridge isn't available in all photoshop versions, only in the CS versions, I use CS2 myself for this tutorial.
Open up Bridge, if you don't have a shortcut for it on your desktop or your quick launch go to START > All programs > Adobe Bridge.
Now browse to the map containing your images you wan't to resize, there's no limit on resizing how many images but it will take longer for more images ofcourse. Your in the map with images? Good, Select all the images (Shortcut: Ctrl+A) This will select all the files in that folder, if the folder has sub-folders then hold ctrl and unselect those folders so you only have the images selected.
Go to Tools > Photoshop > Image processor, this will open up photoshop and pops up the image processor window.
Then select the folder you want the resized images to be saved in, you can select the same folder if you want since the image processor will make a new map "images" in the selected folder, this will keep the resized images in the same folder as your originally sized images, thus making it more organized
leave all other settings default, press run and the image processor will automaticly resize all selected images.
And there you go, you succesfully resized all selected images to 640x480 in a few clicks! I Hope you enjoyed this photoshop/bridge tutorial.