Yes, it's possible to gather a lot of information from systems using SNMP. The only restrictions are that SNMP has to be enabled on the target system, and you have to know the system's SNMP community name (a simplistic form of authentication).
You can certainly write an application that calls the SNMP APIs
directly, but that's not the easiest path. There are many programs
available that query SNMP-enabled systems. If you go to a site like
http://www.download.com/ and search for the phrase 'SNMP', you'll find
many. Good luck.
This was first published in November 2001