Using wget to get the latest module version
The latest stable is published on an XML file, so your script would need to query and parse it to get the proper URL. http://updates.drupal.org/release-history/project-list/all this returns ALL the projects release history, obviously very large. You can get a specific project with this URL http://updates.drupal.org/release-history/views/7.x where "views" is the project name and "7.x" is the version.

Or you could just use DRUSH. It's super easy to install and will make your life 100x easier and better. Drush is a command line PHP script that allows you to simply type things like drush dl views or drush up views. It can do a lot more too, it's truly amazing. http://drupal.org/project/drush