Yup, someone is trying to test me. This is like the gazillionith brake question in the last two to three weeks!!! :crazy:
I'm going to assume that this "squeak" only happens when you hit the brakes, right? Are you sure it's a "squeak" and not a "grinding" sound? I know that the rotors will form a layer of rust (like Mav is saying) when there is enough moisture in the air like rain, mist, dew, etc. Your first few brake applications will grind the rust away, but you will hear (and feel) this grinding. Also, the front outer pads have an anti-rattle clip with a built in wear sensor. What this wear sensor does is when the friction on your brakes get worn down to a certain level (roughly 1/8") the wear sensor (which is metal) will rub against the rotor and will make this grinding sound. Not only can you hear it, but you can also feel it.
So basically, check your pads for wear or even breakage of the friction material.
Let's us know what you find out. If that's not the cause of your noise, than we can dive into further. But checking your pads is a great place to start.