Ixchariot - Instant performance assessment of complex networks from pre- to post-deployment.
UptimeRobot - Free Website Uptime Monitoring
iperf - A TCP, UDP, and SCTP network bandwidth measurement tool
Uptime Kuma - A fancy self-hosted monitoring tool.
Ostinato - Ostinato is a packet crafter and traffic generator for network engineers. Wireshark in Reverse.
Pingdom - With website monitoring from Pingdom you will be the first to know when your website is down. No installation required. 30-day free trial.