Well its nearly 1am - but I've just submitted by very first Drupal module to the community
http://drupal.org/project/globalredirect
Basically, if you have an alias for a node then it will redirect you to the alias if you try to access the node directly… The best example is the site it was designed for. At Sportbusiness.com you could access a news story by:
http://www.sportbusiness.com/node/160374
However if you try that on sportbusiness.com, this module picks up that node/160374 actually has an alias attached to it and you will automatically be whisked away to that aliased URL, in this case:
http://www.sportbusiness.com/news/160374/london-2012-appoints-head-of…
The reason I wanted to do this was because search engines such as Google DO NOT like duplicate pages (ie pages with different URL's but the same content). This could land you in the sandbox! However with this module, if google manages to find a link to node/123456 then wont see the same content as its aliased sister page, instead it will get permanently redirected (a 301 redirect)!