MenuMeters

MenuMeters is a system monitoring tool for Mac computers. It displays real-time information about disk activity, CPU, memory usage, and network throughput.
The program doesn't come with a classic interface as most similar utilities provide.

Instead, it installs directly in System Preferences and shows updated information in the menu bar of your Mac. Therefore, you can easily check the current CPU usage. The information is displayed as a two color-based graph so that you can have a clear view of both user and system CPU usage. The Disk module gives you volume space details about your local drives. The data are updated at a time interval you determine and can be visually displayed as arrows and lights. In addition, you have the chance to monitor the memory usage as a chart, a bar, a history graph, or as used and free totals. Furthermore, you can choose a different color for each type of memory in order to see at a glance details about the active memory, the wired memory, the inactive memory, and the compressed memory of your system. You can also have a visual representation of network throughput as arrows, bytes per second, and as a graph.

In short, MenuMeters displays in the menu bar of your Mac general system information. With this tool, you can see at any moment in the upper bar the CPU usage, the disk activity, the memory consumption, and the network connection in a convenient way, unobstructed by other windows opened on your desktop.