There are a number of Drupal SEO modules to choose from. Here is a summary of the most popular ones to help with your Drupal search engine optimization.

Module	Project Page	Version	Importance	Tutorials
Path	http://drupal.org/ handbook/modules/path	4/5/6/7	must have	Path Tutorial
Pathauto	http://drupal.org/ project/pathauto	5/6/7	must have	Pathauto Tutorial Pathauto Settings Tutorial
Page Title	http://drupal.org/ project/page_title	5/6/7	must have