My website has about 20 thousand product images. Google Page Speed tells me they can be optimized, and it's correct - the difference is huge. Google is able to maintain identical quality and reduce the image size by 70-90%, and Page Speed even optimizes them for me and provides me with a link to the optimized image. This would be great if I only had a few images, but I can't manually update 20k images. I don't want to make any programmatic changes to handle optimization, I'd rather just run all of my images through a piece of software that can optimize them and replace the existing images. I would greatly appreciate it if someone who has been through this before can recommend a good program that can accomplish a job of this size while still maintaining quality. Thanks.
I ended up using a service from Yahoo, SmushIt: http://www.smushit.com/ysmush.it/. It can handle several hundred images at a time. I tried uploading 2,500 and it froze, but had no problem doing 400-500. The compression isn't quite as good as Google's, as Google Page Speed still says it can compress some of them an additional 3-8%, however, I've noticed that Google will sometimes reduce image quality, whereas SmushIt maintained exact quality 100% of the time.