Pathauto

Pathauto automatically creates URL aliases for URL path settings.

Pathauto requires token which will be standard in Drupal 7. I have my own code that creates the URL instantly using Javascript but requires a visit to the URL path Settings text box. Pathauto creates the URL when the page is saved and saves you selecting the URL path settings text box.

My code could be converted to use jQuery for opening the URL path settings area and inserting the text. You would then have the advantage of reviewing the URL before use, something you might want to do in sites with complex URL structures. There is some work towards using something similar in Pathauto, perhaps based on an Ajax call to create the alias. The Ajax approach would give you both a quick visual review of the generated URL and the opportunity to use information from your Drupal database in the URL.