Vector Magic by Stanford University is a free online service that enable you to convert bitmap images into high quality vector images. It is highly useful as it enhances the quality without making blurry.

Right now it supports images in JPG, GIF, PNG, BMP, TIFF format and output in EPS, SVG, PNG.I was highly impressed by the comparison they have shown with Coral PowerTrace and Adobe LiveTrace and based on that Vectormagic seems to perform much better than available commercial auto-tracing softwares .