“Who should I list as a reference?” is a question I receive from time to time. I always tell the individual to choose people who can share details (projects, work ethic, examples, etc.) about their work and who have a very positive impression of you. And finally, be sure to ask their permission before you list them as a reference!
CareerJournal posted a good article about references, whom to ask, what to look for in a reference, etc. Enjoy.