A promising new service that claims to reduce JPEG filesizes by 50% to 80%. I did a couple of tests using JPEGmini Lite, the free version of their OS X app — they also have a web-based version — and the results were impressive. For example, it reduced one 1600px photo from 457 KB to 68 KB (an 85% reduction in filesize) and another 1600px photo from 584 KB to 144 KB (a 75% reduction), with negligible changes to image quality in both cases. (Your mileage may vary, of course.)
It’s easy to forget to optimize your images, now that high-speed internet access has become so common. And yet, reducing image filesizes is one of the best, and easiest, ways to improve your site’s performance. Optimize your site as if people are still accessing it via 56K modems, and you won’t go wrong… especially if you’re designing with mobile devices in mind.