Advisory Check is a program that reads security advisories for you. It gathers security advisories using RSS, RDF, or XML feeds, compares them against the installed software, and alerts you if you're vulnerable. A wide variety of package managers can be queried to detect installed software. Remote systems can be monitored by using the integrated SSH, Windows-RPC, and Nmap support.
Aranha is an application that uses an XML-RPC layer to retrieve information from one or more servers. The type of information gathered is implemented via plugins, and can be displayed or archived in several different ways. The data is gathered in Round Robin Databases (integrated with rrdtool) and can be accessed using a XUL interface available from the system. Plugins are very easy to write.
BigDaddy is a program for monitoring servers. It is similar to Nagios, with the added benefit of also monitoring and controlling the crontab (or any scheduled application) across an entire fleet of servers. The application comes in the form of a daemon for monitoring and reporting as well as an easy-to-use Web-based GUI for controlling monitoring, viewing timelines of incidents, filing incidents and graphing statistics. The application is extensible with any sort of monitoring module and notification is based on a five step escalation process.
Daemonzup is a server monitoring tool that will check if several services/daemons are up on a specific server. It is run from a cron job. If a daemon appears to be dead, it will send email to admins, plus it may also try to restart it. It is designed for GNU/Linux and depends on Perl. It can monitor whatever software is daemonized: apache, MySQL, SSH, cron, xinet, syslog, etc.
FSHeal aims to be a general filesystem tool that can scan and report vital "defective" information about the filesystem like broken symlinks, forgotten backup files, and left-over object files, but also source files, documentation files, user documents, and so on. It will scan the filesystem without modifying anything and reporting all the data to a logfile specified by the user which can then be reviewed and actions taken accordingly.
GResolver is a graphical DNS query tool. It allows system administrators to quickly and easily make the most common DNS queries without constructing lengthy dig commands. It supports all the main resource record types, including AAAA, AXFR, MX, and TXT, and the appropriate in-addr.arpa address is constructed from dotted-quad IP addresses when doing PTR queries. There are checkboxes for controlling the most commonly used options.