Pandora FMS is a monitoring Open Source software. It watches your systems and applications, and allows you to know the status of any element of those systems.

SQL diagnostic manager is a powerful performance monitoring and diagnostics solution that proactively alerts administrators to health, performance or availability problems within their SQL Server environment, all from a central console.

Scalr is a fully redundant, self-curing and self-scaling hosting environment utilizing Amazon's EC2.

"Like monit, only awesome"

The MOle allows you to precisely analyze how your customers are interacting with your rails application.

Nagios is an open source host, service and network monitoring program.

monit is a utility for managing and monitoring, processes, files, directories and devices on a UNIX system. Monit conducts automatic maintenance and repair and can execute meaningful causal actions in error situations.

Some of the best tools for keeping track of buzz online.