ServerSuit - ServerSuit is a browser based program that enables remote Linux administration, monitoring, website hosting, and server setup automation.
S3stat - S3stat is a service that takes the detailed server access logs provided by Amazon's CloudFront and Simple Storage Service (S3), and translates them into human readable statistics, reports and graphs.
Nagios - Complete monitoring and alerting for servers, switches, applications, and services
Qloudstat - Analytics & monitoring for access logs in Amazon S3, Amazon CloudFront, Google Cloud Storage and Rackspace CloudFiles (Akamai CDN)
Datadog - 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.
Checkmk - Checkmk - the software for effective IT monitoring