Crusty punks are those 'old school' punks you tend to find around crowded areas, especially Berkeley. These guys tend to clean themselves rather rarely (thus the name). They usually either are homeless or pretend to be, and are always drunk (in stark contrast to 'straight edge' people). They spend much of their free time dumpster diving or listening to old-school punk music. Crusty punks can also be identified by their leather jackets, 'studs' in their clothing, various tatoos and mohawks or similar hair.
Many crusty punks also have dogs.. it is a mystery as to how they feed these dogs (or themselves)