First, most schools specifically ask for a current supervisor or for a clear explanation of why you are not using a current one. If you don't use your supervisor, the assumption is that you don't believe that individual will support your candidacy. If there is another reason, you need to make that very clear in your application.
Volunteer work can certainly provide a good recommendation...IF...your volunteer work shows your business aptitude. Saying you showed up 3 times to do weatherstripping for Habitat for Humanity won't buy you anything. In choosing recommenders, you need to find people who can say to the school, "I've seen this person operate in a business environment and he/she has great potential because of the following..." Every school has a different format, but they will ask things such as "how well do you know this individual?; "What is your relationship?"; "How does he/she stack up against the other people you have supervised?"; etc. Check out the specific forms for your schools (if possible, some schools won't release the recommendation format) and ask yourself (and your volunteer supervisor) whether he/she feels competent to answer the questions posed.
Professors are less valuable because their perspective will be academic rather than professional. Remember, the goal is not to convince these people that you are a nice guy, but to convince them that you can operate successfully in a business environment.
Tani Wolff
