Best program to optimize hundreds of pictures?

I've been developing a site for the past couple months on my free time, and it's nearly complete, however I did not optimize the PNG images in Photoshop when I made them. 100 of them are 75x32 and, combined, take up nearly 1mb of space.

Is there a program that would allow me to load all the pictures, and compress/optimize them all at once? Doing it one-by-one in Photoshop would be a huge hassle.

Thanks for any help!

photoshop, actions, batch or droplets.