Free Affiliate Link Cloacker
As such I have attached a small php file that you can use and edit for your own needs easily. The code is all explained internally but all you need to do is to edit the list of links.
Just make any changes to the links and upload this file to your server.
Using this you can can then quickly create links such as: http://www.yourdomain.com/specialoffers.php?a=<nickname>
Where <nickname> is the short name you associate with the link that you have in the list (see code)
Hope you find this useful...