liboping is a C library for measuring network latency using ICMP echo requests. It can send to and receive packets from multiple hosts in parallel, which is nice for monitoring applications. Both IPv4 and IPv6 are supported transparently for the programmer and user. A program called oping is included to show the simplicity and potential of the library and provide the functionality at the command line.
GroundWork Monitor Community Edition can give you insight into your computing infrastructure, allowing you to see the current and historical states of all your computers: servers, desktops, and laptops, all of your network devices, all of your services (like TCP/IP and Web services), and all of your applications (like mail servers and database apps). You can choose to be alerted when something goes awry via pager, SMS, email, or phone, and even set up automatic restarts or fall-overs.
Nagstamon is a Nagios status monitor with a UI that resides in the systray or as a floating statusbar on your desktop. It informs you in realtime about the status of your Nagios, Icinga, Opsview, Ninja, Check_MK/Multisite, Centreon, or Thruk-monitored network. It alerts you with sound and visual notification. Failed hosts and services are easy to connect with by SSH, RDP, and VNC. Custom actions can be run on certain events. It works best with GNOME, but also with KDE, Mac OS X, and Windows.
psinfo shows process information and statistics using the kernel /proc interface. This information includes: process state, environment, arguments and flags; CPU usage; scheduling; I/O usage; virtual memory status; pagefaults; capabilities; and signals. psinfo is useful for providing a detailed view of the current state of an application when diagnosing issues or performance problems.
Diskus is a high-level hard drive diagnostic and limited repair tool. It checks the disk geometry by writing numbered IDs into the sectors of the hard drive. Later one can verify that these sector-IDs on the disk are still correct, thereby detecting data which was not correctly written. There is an option to "freshen" the data on your harddrive, which will read and rewrite the sectors. With modern drives this will re-map defective sectors.