Difficulty: 4 - Applied-Intermediate Trick
Siteswap: 3
Prerequisite Skills: Columns, Mills Mess
Watch Video - WMV - 0.8 MB

Boston Mess is Mills Mess juggled in columns. Since the balls never cross over/under each other, you have to do all the crossing with your hands. This is one of those tricks that takes a lot of work to get solid, but it's not that impressive looking to a spectator (less bang for your buck).
Instructions:

You must first be very comfortable with your Mills Mess pattern, and be able to juggle it effortlessly.
Half Boston Mess - We'll begin by learning the "Half" Boston Mess. With two balls in your right hand and one in your left, start off with the right arm crossed over the left arm (like the beginning of Mills Mess). Now, instead of throwing the first ball from the right hand into the center of your body, throw it straight up in a column, then move that hand (still holding the third ball) back to the right side of your body. Then throw the left-hand ball (ball #2) straight up in the center of your body, and move it over to the left side of your body to catch ball #1. Finally, throw the last ball (ball #3) straight up from your right hand, on the right side of your body.
Now repeat. Your right hand will always be on top, and it will make stops at the three positions in this fashion: right, middle, left, right, middle, left, right, middle. Notice that this is a "typewriter" style sweep, meaning it jumps back to the first position when it reaches the end (instead of reversing through the middle position on the way back). Your left hand will always be on the bottom, and it's traveling in the same pattern, still in the "typewriter" style: right, middle, left, right, middle, left. Your left hand though, will be staggered behind your right hand, because it will always be following it catching its throws.
To perform the full Boston Mess, you'll need to alternate which hand is on top. The pattern moves such that a hand is in the top position throughout one "typewriter" traverse (right, middle, left), then it moves to the bottom for one traverse (right, middle, left), then back on top, etc.
This pattern is a bit tricky to learn at first. You will find yourself getting confused as to where your hands need to be at any given time, but after a while, it will become second nature to you. It is a very good feeling trick to juggle, but again, it's not much to look at.