NIXStats - SaaS monitoring tool for window/linux servers and websites. Think up-time robot but with more features.
Obkio - Simple Network Monitoring and Network Troubleshooting software to empower users to identify and troubleshoot network & application slowdown from the end-user perspective.
OpsDash - All-in-one solution for monitoring servers, services, uptime and databases. Curated Dashboards. Rule-based alerting.
SolarWinds Network Bandwidth Analyzer - Download a 30-day free trial of Network Bandwidth Analyzer Pack, easy-to-use software that delivers real-time monitoring, alerting, and reporting for routers, switches, and other SNMP-enabled devices.
Monitornator - Server monitoring made simple
SevOne - SevOne provides network managers with monitoring, troubleshooting, and performance reporting capabilities.