Network Management Resources  

SNMP, SNMPv2, SNMPv3, and RMON 1 and 2 (3rd Edition) by William Stallings.   Good coverage of SNMP versions 1, 2 and 3 and RMON. Its not exciting or thrilling but I recommend it as a reference to any Network management professional that wants to understand MIBs and to developers of NMS products.

SNMP MIBs collection
"We offer a rich database of completely unique, hand-compiled MIBs by our support staff that have been uploaded by our community members over the years"
http://www.oidview.com/mibs/detail.html 

Cisco MIB Navigator
http://tools.cisco.com/Support/SNMP/do/BrowseMIB.do?local=en&step=2
Translate, Search and Download SNMP MIBs (Standards and Cisco specific)
http://tools.cisco.com/Support/SNMP/do/BrowseMIB.do