DownNotifier.com - DownNotifier knows about website availability and provides notification.
Ping Meter Gadget - Customizable, graphical, semi-transparent ping (latency) meter.
UptimeRobot - Free Website Uptime Monitoring
SmokePing - Smokeping is a tool for measuring latency.
Is It Down Right Now? - Network & Admin
PingInfoView - PingInfoView is a small utility that allows you to easily ping multiple host names and IP addresses, and watch the result in one table.