Progress bars add color and at-a-glance understanding to a list; far better than a small gray percentage number. Once again we're plundering Christophe's solutions; this time it's his formula for a progress bar:
="<DIV style='background-color:red;'><DIV style='background-color:LimeGreen; width:"&([% Complete]*100)&"%;'><img src='/_layouts/images/blank.gif' /></DIV></DIV>"
No need for JavaScript or Content Editor Web Parts: Simply paste the above formula into HTMLCC's formula box, adjust the colors in bold above (not everyone's a fan of Lime Green), and save.