BSNMP is a portable SNMP framework consisting of a daemon (bsnmpd), modules and tools.
Most of this work is also part of the FreeBSD source tree and shipped with FreeBSD releases.
You can find some more information about BSNMP here: http://people.freebsd.org/~harti/bsnmp/
In addition to that there are various pages on the wiki: CategorySNMP
We are always looking for people to help implementing more modules and tools for this framework to enhance usability of BSNMP. Check out the TODO list: BsnmpTODO