Image optimizing is a good thing every web designer should do. It will make the image load faster and save bandwidth. There are many tools available to perform this task, the free and perhaps the easiest one is Smush.it.
Adobe Photoshop is a great graphics/photo editing program but it is expensive. Most people especially freelancers like me aren’t able to afford it. Luckily I found GIMP (GNU Image Manipulation Program), it’s open source software free for personal and commercial use. I’ve been looking for and trying to use many graphics editing programs for years, but now I will stick to GIMP. Because it’s really has some good reasons to love it.