Were the rotors turned or replaced ? If not, then that's probably your problem as warped or bad rotors will cause a shake when braking. I would have that checked at where you had the brakes done as they should warranty their work. I would also get a front end alignment and have the bearings checked out. But I'll bet it's one or both of the rotors.
It could be that your breaking too hard for the tires to handle but it could also be an internal problem.