NIXStats - SaaS monitoring tool for window/linux servers and websites. Think up-time robot but with more features.
Qualys - Qualys helps your business automate the full spectrum of auditing, compliance and protection of your IT systems and web applications.
SolarWinds System Management - Performance monitoring and management for applications, Websites, servers, storage arrays and virtual infrastructure.
Burp Suite - Burp Suite is an integrated platform for performing security testing of web applications.
Nodeping - NodePing Server Monitoring and Web Site Monitoring. Simple but powerful Internet service monitoring.
OpenVAS - The Open Vulnerability Assessment System (OpenVAS) is a framework of several services and tools...