What exactly do you mean by 'task navigator'?

If you want to see what's running, you can install the CPU task bar application, and there's a drop-down that will show a few running processes, and memory hogs.

If you install Osso Xterm you have access to the *nix tools 'ps' and 'top', which will show you everything running (ps), and a real-time list sorted by CPU usage (top in default mode). Top has interactive options, and ps has command line options.