Yes. We have an API (NOW WITH SSL!), get over it. We have two ways you can shorten an url using this API:

The HTTP-Request-URI Method
Request Syntax: https://x0.no/api/?[Long URL] (e.g: https://x0.no/api/?http://x0.no)
Request this URL with a "?" and your address, and you will recieve your shortened URL as a response
This should work for most people, unless you have really weird URLs.

The HTTP-POST Method
Just post the POST-variable "u", containing your Long URL to https://x0.no/api/post
And it will reply with your shortened url!