Check out the Data Everywhere API.
Scrambles a progressive integer (DB index?) into a unique string like Bitly, TinyURL and Youtube do. Example: if you input 20 you get "YvfCww" while inputing 21 you get "Ln4kQ9" and so on... You can also specify your own seed. Use it for very custom short URL generation or anything you like, it is free.
Connect to API