A good rolling boil is important for a good beer. Lots of good stuff happens during the boil. Volatile, smelly sulfur compounds are expelled from the beer. Other compounds, alpha acids, that bitter our beer are only extracted by boiling. But get too vigorous a boil going, and you'll slop wort all over the place. Instead, try using your marbles.
That's right, glass marbles, the kind kids play with. Just put about 20 of them in the brew pot. Don't worry about the marbles breaking. There're made of tempered glass and their spherical shape gives them great strength. That's why kids can bang them together day after day and they don't break. Don't worry about the heat, either. A few hundred degrees Fahrenheit is nothing to a tempered glass marble.
Instead of getting big, explosive gas bubbles popping up and blowing beer out of the kettle, you'll see a bunch of smaller, finer bubbles evenly spread over the center of the boil. This steady stream of smaller bubbles will do just as good a job of breaking up the hop resin and oil bubbles in your wort -- without the sloppy mess.
A Phantom Brewer had this problem early on and greatly smoothed out the boiling by adding about 20 glass marlbes to our 15 gallon brew pot.
The Phantom thanks Sal Sciortino for retaining enough marbles to pass this tip on!