Just so people know that my 2007 service manual on page 8L 96 says that the brake light switch is only available as an assembly with the "power brake booster". It does show on page 8L 90 or 8L 91 in other years manuals how to replace the switch. The MB switch on my 2005 is # 001-545-64-09 and SMP (Standard Motor Products) # is SLS384. Much cheaper than the brake power booster!
You can also check your brake relay in the underhood fuse panel - you have to remove the second cover to see the relays that are closer to the windshield - the relay is MB # 0025421419 and SMP # RY1091 (it's the Yellow one) and the fuse #2 in the ICM (Illumination control module connected to the headlight switch) I think those are the main things to look at if your brake lights don't work and your bulbs are ok. Hope this clarifies the info out there.