Bartlby is a network and system monitor, completely written in C, to provide a scalable framework with the ability to monitor networks of various sizes. It consists of a core daemon, several plugins, and a Web GUI (PHP extension). The core daemon checks (over active/passive TCP) services/hosts and notifies users in case of critical service conditions (mail, SMS, ICQ, and custom triggers are supported). Bartlby provides an open plugin interface to give every administrator an easy to use option to extend the plugin base, and a fully customizable GUI (written in PHP using a C extension). Nearby everything can be controlled via an XML interface.
UnusedPkg is a diagnostic tool to search the oldest unused packages in your Linux system. UnusedPkg prints a sorted list with the size and number of days that a package has been idle. This helps you determine what packages can be manually removed to clean the system. It supports any apt-based distribution (tested on Debian and Ubuntu) and Slackware.
Raven's System Stats allows users to collect detailed information about an operating system, including kernel architecture, distro, operating system, kernel version, glibc version, name of login shell, number of CPUs, CPU description, hyperthreading support, CPU MHz, CPU cache, bogomips, used and total RAM, used and total swap, filesystem size and type, uptime, unique users logged in, total login shells, currently running processes, total processes since bootup, load average, X resolution, and the number of X servers running.
CaiCai is a network and services monitoring system. It performs tests for ping, DHCP, POP3, SMTP, FTP, etc. It does not require additional software installed on the remote side. It is fully configurable. It provides instant reports (via an HTML page), logs, statistics, and sound alarms.