Smush It

This is a handy little tool for anyone creating or maintaining websites or blogs (which isn't just developers these days). Yahoo! has a free web-based tool called Smush.It that will convert any JPG, GIF, or PNG file to a smaller, more compressed version. This means faster downloads and lower bandwidth requirements for your site (and $$$ savings, depending on your hosting service). Plus it's just plain nice to do for your site visitors - nobody likes waiting around for pictures to load, especially on slower mobile devices. Smush.It can achieve up to a 70% reduction in some cases, without any quality loss. Not bad for free.