NIXStats - SaaS monitoring tool for window/linux servers and websites. Think up-time robot but with more features.
GTmetrix - GTmetrix is a free tool that analyzes your page's speed performance. Using PageSpeed and YSlow, GTmetrix generates scores for your pages and offers actionable recommendations on how to fix them.
SolarWinds System Management - Performance monitoring and management for applications, Websites, servers, storage arrays and virtual infrastructure.
PageSpeed Insights - PageSpeed is addon for ...
Nodeping - NodePing Server Monitoring and Web Site Monitoring. Simple but powerful Internet service monitoring.
WebPagetest - Run a free website speed test from multiple locations around the globe using real browsers...