Artiss URL Shortener will shorten a supplied URL using one of over 80 different shortening services
Just let me know and I'll include it in a future release if it has a compatible API that this plugin can access.
I used to include them on this README but they change so often it's difficult to maintain. So, after version 2 an administration screen is included which lists all the services, as well as which additional parameters are required for them to work (e.g. API key, etc).
The original, long URL is returned if the short URL could, for whatever reason, not be retrieved. Please ensure you have specified the service name correctly and supplied any additional information that the provider requires (e.g. API key).
It has been tested and been found valid from PHP 4 upwards.
Please note, however, that the minimum for WordPress is now PHP 5.2.4. Even though this plugin supports a lower version, I am not coding specifically to achieve this - therefore this minimum may change in the future.