Read original post by Johan Silfversparre at JayWay Team Blog
I am working on a Windows Store app where one of the features is to share shortened links. This is a brief description on how I solved it.
Bitly
You can find a long list of different link shorteners at Programmable Web. I will use Bitly mostly because I used it before with success. The signup process and app registration is easy. Here is a blog post describing it in detail: Bitly API: Authentication.