Caesium Image Compressor is a free, open source image compressor that can reduce the size of your pictures up to 90% without losing from the original quality. You can use this program for many purposes: save space on your hard drive, reduce the size of images so that you can upload them faster on various websites or blogs. It is a valuable tool for webmasters/bloggers/photographers who look to optimize their collection of images in order to reduce the loading time for their website visitors. This software will allow you to view compression results which is useful especially when you don't know which optimization type you need (it has several different compression levels available). It is currently available in 2 flavors as a Windows installer (setup) and portable.
Click here to download Caesium Image Compressor