App Tamer goes beyond throttling and will actually put applications into suspended animation. It also will tackle any program that you wish, not just limited to browsers. By default it will pause resource-heavy apps such as Photoshop and Chrome when not in use, saving all but a tiny percentage of their CPU usage.
Configuration options include the ability to put a shadow mask over paused programs, helping to identify them as suspended. You also can define the period of activity before App Tamer does its thing. App Tamer will wake the paused app with user-configurable time periods, which by default is every 5 minutes. This helps prevent the app from crashing out.
When you switch back to a paused application, App Tamer resuscitates the program with almost instant results -- there didn't seem much in the way of perceivable lag in my testing on a 2011 MacBook Pro. Everything then runs normally until you click away, putting the app back into suspended animation.
In my rather unscientific testing, App Tamer more or less killed all CPU demands of paused applications. This led to much more free resources without the need to kill the apps when not in use. Your milage, as they say, will vary -- but a free trial is available, so you can see whether it's going to do what you need without commitment.
So, if you're looking for something that goes beyond just browser throttling -- App Tamer will set you back $15 and should help you reclaim CPU-cycles, reduce heat and increase your multi-tasking battery life.
Hat tip to Mystakill