I’m not sure how often I’ll use URL Shorteners now that I’ve discovered markdown. But I’m sure I’ll use them occasionally. I found 2 shorteners than run on software licensed under the GPL (I’m not sure why the AGPL was not used).
TightURL Or use TightURL’s mirror: 2tu.us
The other site I found is ur1 Generator
I wonder if there is an easy way to use a personalized URL Shortener on your own server with a your own domain (e.g. link.glodime.com/1qaz).