I am currently working on software that must emit SNMP traps for SNMP versions 1 & 2 and possibly v3 in the future. I have downloaded several and found them to be either too complex or too simplistic. All I want is to view traps and analyze the data structures within them, and the ability to import my custom MIB's. The best I have found so far is ireasonings MIB Browser, but would be greatful for any nice alternatives.
netsnmp - should do everything you're after, with a variety of language bindings to suit every taste.