What tool could I use to limit processor time for specific web site running under IIS on windows web server 2008?
You can limit CPU Time by giving that website its own application pool and configuring it accordingly:
Unfortunately this does not provide a peak, where it would cap the worker process and allow it to run at 100% of your defined limit (say 60% of CPU is your limit). Once it hits your defined limit it executes a defined action of "log" or "kill process".
I am curious as to why you would want to cap the process? If you have IIS related processes eating up 100% CPU you may be better off investigating that issue. You could use the Debug diagnostics tool to troubleshoot:
You can get greater granularity over IIS and just about any other process using the Windows System Resource Manager.