This package interfaces with the Bit.ly URL-shortening REST API (www.bit.ly).  
It implements all the API methods documented here: http://code.google.com/p/bitly-api/wiki/ApiDocumentation#REST_API

Example:
    $b = new Bitly('mylogin', 'API_KEY');
    echo $b->shorten('http://www.google.com'); // "http://bit.ly/SD3eqa"


The PHP is well documented and will hopefully suffice for now.