Hello !
A few weeks ago I had to resize about 15-20 pictures.
"OK, a lot of images, a lot of time waste to save all of them" I said.
After using File > Save for Web and Devices for about 3 images I thought that there must be an easy way to do that. And I start searching on Google. :)
And the easy way is Image Processor.

Then make the following settings :

Quality is for the image quality and is between 0 and 12.
Don't forget to check the "Resize to Fit" check box, and for the width and height insert the values io need.
Press Run and Photoshop will start resizeing and saveing your images.
Hope this post was useful for you !