Easy Image Modifier provides free, easy batch image processing
Easy Image Modifier is a simple piece of portable freeware that can rotate, resize, convert, and rename JPG, PNG, and BMP files.
I tested it with a bunch of large JPGs (about 1.5MB each). I just dragged the JPGs over it and dropped them. Then, I set the Resize option, set a destination, and clicked the huge button up on top (the one that says "Drop images here." Once you drop them, its text changes to say how many images you've selected and that you have to click it to start).
What can I say? It works as advertised. I like the simple, sensible UI and the fact that it's portable, no-frills, and absolutely free. There is a paid Plus version, but besides the tiny menu item that says "Plus!," you will see no mention of it within the program. Oh, and I also like that it doesn't add anything to the file context menu.
I will be sticking with IrfanView, but if you don't currently have an easy-to-use image converter, you could do much worse than this one.