Pathauto is one of my preferred modules for developing blogs using Drupal.
The Pathauto module automatically generates path aliases for various kinds of content (nodes, categories, users) without requiring the user to manually specify the path alias. This allows you to get aliases like /category/my-node-title.html instead of /node/123. The aliases are based upon a “pattern” system which the administrator can control.
If you are a Drupal-5 experienced user you will notice that version 6 lacks of a “Administer – > Site Configuration -> Pathauto” menu link, like the older versions had.
Where (the hell) is this menu? Here is a quick tip:
For 5.x: Administer > Site configuration > Pathauto For 6.x: Administer > Site building > URL alias > Automated alias settings