In the wake of the overflow of megabank mergers at FleetBoston, Citizens, and Sovereign BankCommunity, community banks in Greater Boston have an enormous opportunity to gain new customers. To undercut the competition, many community banks are offering lower fees, free checking, and even freebies, such as a $50 bonus check, baseball caps, or binoculars. Banking analysts agree that community banks are in a good position right now because they provide local service and can give quick responses, especially to small businesses. According to the Massachusetts Bankers Association, gains in deposits and loans are being posted by banks in Essex and Middlesex counties. Julie Ganong, a Provident Bank spokeswoman, said the mergers offer the opportunity for the community banks to show that they offer the same products as the large banks, but with better service.