http://www.gourdoughs.com/
http://www.fracturedprune.com/specialty.php
http://doughnutplant.com/menu/
Also, look at doing some 'healthy/alternative' type of donut of the day or something. Get the health conscience folks in there with those and some specialty/organic coffee or tea options.
I would definitely suggest "special" donuts such as a maple and bacon donut. Makes your place a 'hot spot' when someone wants a specialty donut like that. DD can't compete with something like that :)
Good luck to you!