SEF URLs in Drupal 7.7?
Go get pathauto http://drupal.org/project/pathauto
With pathauto you can set up automatic path aliases to do exactly what you want. It will basically allow you to set up patterns for how to build token based paths for new pages at the time of their creation. It's one of the most widely used Drupal modules and is an absolute necessity for any site.

Also, once it's enabled and you've set up your paths the way you want them you can regenerate existing aliases in bulk at the content overview page.