I don't think there are actually that much differences between different tools, because the JPEG compression is standardized. If your default image tool (I prefer GIMP), supports a level-based compression control, you just need to figure out how much details you are willing to lose. Here is a good article on that:
<a href="http://www.codinghorror.com/blog/2006/07/a-comparison-of-jpeg-compression-levels-and-recompression.html" rel="nofollow">http://www.codinghorror.com/blog/2006/07/a-comparison-of-jpe...</a>