Such as
Realtime CPU graphs and a list of the top 5 CPU resource hogs. CPU usage can be tracked by individual cores or with all cores combined, to save menubar space.
Memory
Memory stats for your menubar, shown as used and free memory or wired, active, inactive and free. The memory dropdown menu shows a list of the top 5 memory hogs, as well as other useful info.
Network
The realtime graph will keep your finger on the pulse of what data’s being sent and received for all network connections.
Disk Usage
See used or free space for multiple disks in your menubar. More detail for all your disks is only a click away.
Disk Activity
Detailed disk I/O in your menubar, including a variety of different read and write indicators.
Sensors
Realtime listings of the sensors in your Mac, including temperatures, hard drive temperatures (where supported), fans, voltages, current and power. Temps can be displayed as Celsius, Fahrenheit or Kelvin.
iStat Menus is available for free to download, but if you’d like to see it continue to be developed then please either donate or check out our iPhone apps.
Date & Time
A highly configurable date and time for your menubar, a calendar with week numbers, and a world clock with a database of over 20,000 cities—it’s one of the most powerful replacements for Apple’s date and time menu available.
Complete control
Each menu extra comes with many different display modes, each featuring customizable colours, font sizes and
Another cool deal from the iSlayer is a istat widget
