You mean you want something that will show the memory and cpu of individual sites? If you're running your sites in dedicated application pools (and you should be) take a look at the task manager, add the PID column and you should be able to identify which app pool / worker process is consuming the memory and cpu.
I also like to use process monitor from sysinternals for this. The other thing you can do is fire up file monitor (also from sysinternals) and see if you see any odd.
Give us a little more info on what's happening and we can probably help resolve it.