measuring mysql usage

[John Almberg]

Anyone know of a tool that can measure mysql usage per mysql user?

My database is getting hammered by something, but I'm having a hard  
time figuring out what. It seems to come and go. Perhaps I have one  
or two websites that are just getting a lot of traffic, and maybe  
they just need their own machines. I'm not sure, which is why I'm  
looking for ways to start monitoring these sites and their resource  
usage - particularly db usage - more closely.

Any thoughts or tips, much appreciated.

Thanks: John