Free image resize tool

I use ACDSee 7.0 to perform this, you can also use create a resize action then use batch actions in photoshop and save them in a different folder and keep the originals
(file--->automate--->batch) or you can create a droplet which will perform an action (file--->automate--->droplet) I recommend playing with the settings on a file you dont much care about or a copy just to be sure you have them right.