I just found a simple little utility to resize entire folders of photos quickly and easily. It’s free, it doesn’t need an install, and it works pretty well.
The unusual part about it is that it works differently depending on what you name the executable. You can see what I mean by reading the information on the developer’s website. But basically, you use their online tool to generate a filename for their executable, based on what your requirements are, then you download the program and change the program’s name to whatever their online tool gives you. Then, simply drag a folder full of pictures onto the executable and watch it work!
I just tested it at the school that I’m working at today and it’s pretty amazing. It dropped the total size of a folder of pictures (124 of them to be exact) down from 174MB down to 12.5MB. I had them resized to a screen-friendly and web-friendly 1280 x 851 pixels (although I set it to 1280 x 1024).
You can do the same thing with other software, but most are more complex to use and cost lots of money, sometimes in upwards of $500.
Give it a shot! http://www.rw-designer.com/picture-resize