OpManager is a commercial NMS Product. It's far to be perfect, but it is (very ?) cheap, cool, and sweet.

Here some tips :

==Use Telnet/SSH based resource monitor instead SNMP==

//You can use the Quick Configuration Wizard (QCW) to associate the Telnet/SSH based monitors to 10 servers. Use Admin -> QCW -> Add a monitor -> Resource Monitors -> Telnet/SSH based monitors for Solaris -> Memory Utilization option.//

Personal note: I have trouble to do that SSH based, but it works perfectly with telnet, it's strange..