This might be useful for some of you. It was recommended this week on BBC's Click program. It's an image optimizer site. You can upload an image and change it to what you want without losing quality. I didn't know where to put it. There should be one page here with a list of useful photography links with short explanations. If there is paste this link there..

Online Image Optimizer: Optimize your GIFS, JPGS, and PNGS online.