VarieDrop is an interesting tool which makes it easier to resize multiple images in a single operation.
The program works by allowing you to define up to four "drag and drop areas", each of which has its own output settings. These include format (BMP, PNG, JPEG, GIF, TIFF), JPEG quality, the target dimensions for resizing, a string which you'd like to append to the file name (_800x600, say), and an output folder. Once you've configured the program to suit your needs, just select your target images, drag and drop them onto that area, and they'll be converted and resized accordingly.
There's also a fifth "drag and drop area" which can optionally combine the results of the others. If you've set up the main areas to create 320x200, 640x480, 800x600 and 1024x768 images, for example, you might also have this fifth area generate all four sizes in a single drag and drop.
VarieDrop doesn't have the power of the leading batch processing tools. You can't rotate your images, add watermarks, apply special effects or do anything else particularly advanced. The ability to resize or convert images by dragging and dropping is a significant plus, though, and if your batch processing needs are simple then the program could be worth a look.
It's a little short on image processing power, but VarieDrop's drag-and-drop interface does make it very easy to batch resize and convert your photos.