iStat nano 2.01iStat nano... An advanced system monitor in a tiny package. View detailed information on CPU, memory, hard drives, IP and external IP, bandwidth, CPU temperatures, fan speeds, battery, uptime and the top four processes. iStat nano features the lowest CPU usage of any stats widget we've seen (compare it if you don't believe us, I'm sure you'll be pleasantly surprised!).
(Via MacUpdate - Mac OS X.)