A very simple and straightfoward CPU/Memory monitor.
Apache Server Watcher
Apache Server Watcher [ASW] is an application, which monitors networked communication systems [Apache, MySQL, etc.] by means of the predefined sensors or user-defined scripts.
ARDMonitor shows the state of Apple Remote Desktop (disabled, enabled, connected) - even if the Administrator asked for permission to monitor/control (that's what ARD's menu extra doesn't).
Changes Meter is a compact menubar item for easy monitoring of remote URLs or local files.
Cheesy Little CPU Meter
A Cheesy Little CPU Meter.
Coconut is an elegant and effective bandwidth monitoring application. Features include automatic detection and monitoring of active network devices. An absurd amount of visual customization is possible, thanks to the DAFTLabelView and DAFTGraphView classes from DAFT.
CPU History is an application that graphs your current CPU usage history in the Dock icon, and optionally in a floating window. You can customize colors, update frequency, and bar thickness.
Dash Monitors is a Widget that runs under Mac OS X Tiger's new Dashboard functionality. Dash Monitors displays a graphic summary of your system resource usage including: CPU usage, Memory usage, Network bandwidth, and Disk read and write speed.
File Monitor allows you to be notified of modifications occurring to any kind of files.
fseventer observes filesystem changes using the same underlying API as Spotlight.
(commercial) Hardware Monitor is an application to read out all accessible hardware sensors in Macintosh computers. Currently more than 100 different Macintosh hardware sensors and more than 200 hard drive temperature sensors are supported. The program can visualize the history graphs of the readings, display measured values in a large variety of fashions, or announce readings by speech output. It can also store and export readings.
Hardware Monitor Remote
(commercial) Hardware Monitor Remote allows you to use a hardware monitoring service on a remote Macintosh system. Other computers can contact this system via network (local area network, wireless network or the Internet) to receive readings from all available hardware sensors.
iCPU shows your CPU load. It is a nice icon in the Dock that changes with your CPU load, while eating very few resources itself.
Internet Traffic Report Widget
The Internet Traffic Report Dashboard widget shows you the latest traffic report from www.internettrafficreport.com. This free service provides a graph of the response times (higher peaks mean slower global responses), the global index (higher numbers mean faster Internet), and the current global index trend (rising, falling, or steady).
(commercial) Using its concise and pleasing user interface, iPulse graphically displays the inner workings of Mac OS X on the desktop or in the dock. The entire user interface is completely configurable so you can turn off gauges you don't want, leaving only what you are interested in for easy viewing.
iStat nano is an advanced system monitor in a tiny package. View detailed information on CPU, memory, hard drives, IP and external IP, bandwidth, CPU temperature, battery, uptime and the top four processes.
a simple cpu load monitor for MacOS X
LoadInDock is a tiny application which shows the CPU load in the Dock.
MacFace is an activity monitor that shows CPU and RAM utilization via a cute, generally anime-style face in your Dock. It goes a step farther than just showing current CPU load by indicating low-memory (heavy paging) circumstances by having the face in the Dock look more stressed.
(shareware) Measles provides you with little bouncy spheres on your desktop which are fun and colorful. They can be configured to act as CPU monitors, changing color according to how busy your machine is, or they can use a wide variety of color schemes and fill patterns.
Memory Monitor is a small application that displays the memory usage in its Dock icon (and optionally in a floating window), like CPU Monitor displays the CPU usage.
MemoryCell is a MenuExtra for OS X that provides a quick overview on the memory (RAM) being used by each of your applications. With MemoryCell, you can monitor the memory usage of the foreground application, using this knowledge to restart anything that's started to bog down your system.
MenuMeters is a set of CPU, memory, disk, and network monitoring tools for MacOS X.
mkconsole is a little application that displays logfiles on your desktop. It is useful if you have to monitor servers or you just want to keep an eye on what's going on on your machine
Nageographer is a graphical utility to aid in positioning icons on the status display maps in Nagios (a network monitoring tool). Nagios, as shipped, requires you to enter coordinates for each icon you want displayed on the status map. This utility lets you drag the icons around where you want them and will save your coordinates back to the config file for you.
(commercial) NetCheck is an OSX native application that provides an array of network monitoring, email alerts, logging, and reporting features
NetStatInDock is a little application which shows the network statistics in the Dock.
Network Screenshot is a utility for watching regulary updated screenshots from another computer.
Notification Watcher is a small application that monitors all Cocoa distributed and workspace notifications and displays them in an easy-to-use list.
Observation Post observes changes in: Bonjour, Network, Sleep, USB, FireWire, Volumes, Files, Folders, Smart Folders - uses Growl to post notifications.
Peek-a-Boo is a utility to monitor and manipulate all running processes. You can watch how much CPU time each process uses, adjust processes? priorities, and monitor process information.
(commercial) RAID Monitor is a utility that you can install onto your Macintosh to monitor the state of your software RAID. If the software detects a problem with the RAID set - it will email you to let you know that there is an issue you need to resolve.
RaidEye is a tool for monitoring Mac OS X software RAID volumes status. RaidEye is able to detect if a RAID volume has damaged or missing members, and can alert the user with a repeating sound and sending an email with a detailed report of RAID status.
ReMon is a remote process monitoring and control solution originally developed as an in house tool to monitor multiple tomcat instances it evolved into a complete product. it's written from scratch in Python and uses push client/network concept.
Server Scout is an application, which monitors networked communication systems [Apache, MySQL, etc.] by means of the predefined sensors or user-defined scripts.
SystemLoad is a diagnostic application assisting you in the detection of cooling or power supply problems with Apple Macintosh computers. The tool can put a user-definable load onto one or more processors. This can help in diagnosing the following issues: problems with the cooling system or temperature sensors, problems with chirping noise experienced on some G5 systems and some portable computers, problems with battery units of portable computers.
Temperature Monitor is an application to read out all accessible temperature sensors in Macintosh computers. The program can visualize the history graphs of the readings, display measured values in a large variety of fashions, or announce readings by speech output. It can also store and export values.
ThermoInDock shows values of the internal thermal sensors on your Mac in the Dock. It also supports the modules to change the appearance of Dock icon.
(commercial) a native GUI-based logfile analyzer for OS X
webPageMonitor monitors websites for changes.
WindowWatcher records to a SQLite database which window and application is in front of all others. The data can be exported in tab-delimited or Property List (PLIST) format.
displays the load of the processor on Mac OS X
XMonitor allows you to easily monitor your disk, cpu, ram and network usage, PPP status, IP address, Email, and more. XMonitor can also monitor the status of up to 25 remote servers via http or ICMP ping requests. XMonitor can automatically generate HTML reports of past and current activity and graph past performance for up to 30 days.