Argus is a system and network monitoring application. It will monitor nearly anything you ask it to monitor (TCP + UDP applications, IP connectivity, SNMP OIDS, etc). It presents a clean, easy-to-view Web interface. It can send alerts numerous ways (such as via pager) and can automatically escalate if someone falls asleep.
pv (Pipe Viewer) is a terminal-based tool for monitoring the progress of data through a pipeline. It can be inserted into any normal pipeline between two processes to give a visual indication of how quickly data is passing through, how long it has taken, how near to completion it is, and an estimate of how long it will be until completion.
Report Magic is an add-on for Analog, a Web site logfile analysis program. Generated reports include a description with tabulated, graphed, and summarized results. All colors, fonts, and background images are completely customizable to help make resulting reports fit the theme of your Web site. Report Magic has translations for several languages. It runs on any platform that will run Perl and pre-compiled versions are available for Win32 and Mac.
bcnu is a Web-based system management tool which delivers information on the status of networked systems in a simple and easy-to-use manner. It uses a web browser to display information about hosts in a tabular form. Historical information can be held indefinitely, and there is a powerful query tool available to interrogate it. Client systems can run an agent which logs information back to a central system. An agent scheduler is integrated to allow agents to be run at different intervals. Standard agents include ftp, http, disk space, logfiles, processes, and more.
IOG is a network I/O byte grapher made to graph cumulative KB/MB/GB totals for hours/days and months. It is intended to be simple, fast (support thousands of interfaces) and integrate well with MRTG (not required). Data for each host is updated hourly and HTML graphs are created. It uses a data consolidation algorithm which allows for a small, non-growing database file for each host. Perl is required, but no external graphing libraries or binaries are needed.
Spong is a simple system-monitoring package. It features client-based monitoring (CPU, disk, processes, logs, etc.), monitoring of network services, grouping of hosts (routers, servers, workstations, and PCs), host-specific contact and downtime information, configuration on a client-by-client basis, results displayed via the Web, history of problems, messaging (via email or pager) when problems occur, and verbose information to help diagnosis problems. It communicates via simple TCP-based messages, and is written in Perl.
Chronic is a constraints-based opportunistic application-level scheduler. Unlike cron, which schedules according to a time specification, it schedules tasks when specified constraints are met. In other words, it schedules during a window of opportunity when the circumstances are favorable.