ManageEngine OpManager is a comprehensive, easy to use and affordable Network, Systems and Applications monitoring software that offers integrated fault and performance management functionality. It is an ideal network monitoring software for WAN monitoring, LAN monitoring, Windows Services & Event Log monitoring, URL monitoring, Server management and Application management. OpManager automatically discovers and maps resources across the network and presents an integrated view of the enterprise in a single NMS console. OpManager actively monitors the network and notifies operators by email / SMS when a fault occurs. OpManager provides reports and graphs for Interface statistics, CPU, Memory, Disk statistics and service response-times and availability. OpManager provides more than 160 out-of-the-box graphs to manage Cisco devices, MS-Exchange, Lotus Notes, Oracle, MSSQL, Dell and Compaq servers. It also supports adding custom graphs to monitor any SNMP parameter. The 10 Node Small Network Edition is available Free of cost. The file weights ~ 26 MB. You can get more information here. Screenshot can be found at this place.