Photoshop, menu File/Automate/Batch...
There, you can select the IN folder, and OUT one...
You have a field to choose which Action (is like a macro, you previously must have created one) to perform over all the files in input folder.
Hit the button and that is it. It will take some minute, but thousand times faster than by hand: often also you need batch operation with psd layers and complex layer modes and groups kept, not possible with external programs.
There are many tutos in internet on how to make a Photoshop action, but basicly, you just hit certain "rec" button in Actions panel, type a name for the action, do whatever needed in Photoshop, and then hit stop bottom. You can then execute that action over any file, or set it in the "Automate" proccess I told you above. Just remember: when doing an action for this, you'd better not do very specific steps, that will not work for a bunch of different files, or may stop with an error.
For my video game graphics, I used this quite a lot, for sprites, tiles, etc. A life saver.
Like always, better if you use PNGs or PSDs as sources, you can include in a certain way the output as JPGs (for formats output I tend to prefer the mentioned here Irfanview, but all can be done. )