Why does Google Chrome Helper spike my CPU?
The problem, in my case, seems to have been one of the tabs I always have open runs some crazy cpu-intensive plugin for ads (I suspect Grooveshark, but am not positive).

The fix was to go into Chrome settings (settings > content settings > plugins) and choose Click To Play.  By default Chrome runs all plugin content as soon as the page is loaded - regardless of what is is, or how much memory it takes.