1. See metrics from all of your apps, tools & services in one place with Datadog's cloud monitoring as a service solution. Try it for free.

  2. Complete monitoring and alerting for servers, switches, applications, and services

  3. Graphite is a highly scalable real-time graphing system.

  4. Your monitoring infrastructure in the cloud. Store, visualize and alert on all your metrics at all levels of the stack. Get your 30d free trial.

  5. Site24x7 offers both free & paid website monitoring services. Monitor websites remotely and receive instant email/sms alerts if your website becomes unavailable. View uptime & performance graphs of your website monitors.

  6. Simple daemon for easy stats aggregation.

  7. Icinga is a fork of Nagios and is backward compatible.

  8. All-in-one solution for monitoring servers, services, uptime and databases. Curated Dashboards. Rule-based alerting.

  9. Amazon CloudWatch is a monitoring service for AWS cloud resources and the applications you run on AWS.