There are many professional bodies that offer accreditation to photographers, and each of these bodies often has a graded level of accreditation. It can be very confusing to understand exactly what the letters after someones name mean!
Of course, some photographers have degrees, and that is easy enough to recognise, just the standard BA or BA (hons) after their name. Some of the other organisations that offer accreditation are: The MPA SWPP (BPPA) RPS and BIPP.
More information about the awards and distinctions that they offer can be found at their websites.