Most people wouldn't be brave enough to go to a barber school, however HVBI is one that you should definitely check out.
For $4 (plus a tip) you get a haircut from the next available student. I found that the students are so focused on doing a good job that they end up giving some of the best haircuts around. The students check in frequently with their instructor Seneca (who is a REALLY nice guy) and he makes sure that they do a great job.
They often have coupons or specials that push the cost of the cut down to $2-3.
Neighborhood barber experience, high quality, great service.