Glsof!

Resource Monitor is a system application in Microsoft Windows operating systems. It is used to view information about the use of hardware (CPU, memory, disk, and network) and software (file handles and modules) resources in real time. Resource Monitor is available in Windows Vista and onwards only (In Windows Vista, it is known as Reliability and Performance Monitor). Resource Monitor can be launched by executing resmon.exe (perfmon.exe in Windows Vista). It was also on Windows 95, 95 OSR, 95 OSR2, 98, 98SE, ME, and NT. »

Sysdig is open source, system-level exploration: capture system state and activity from a running Linux instance, then save, filter and analyze. Think of it as strace + tcpdump + lsof + awesome sauce.With a little Lua cherry on top.

vtop is a graphical command-line tool that uses unicode braille to chart CPU and memory usage. It can be easily extended.