Brakes were working fine when I drove home from work last night. When I got in this morning and hit the brake to put it in reverse it mashed all the way to the floor and the brakes wouldn't work at all. I checked under my car and there was brake fluid pouring out from under the car on the driver's side. Any ideas what may have happened or what needs repaired?

 

Chances are that you have a brake hose or line that failed. Try to pinpoint where the leak is from, very easy to spot. Brakes hoses are pretty easy to replace , but brake lines should be replaced by a professional. Make sur to have the brake system bleeded after you replace the hose.
The cause, Brake hoses fail from the inside out due to the rubber that weakens with time . As for lines , its from the outside in due to rust , usually found where clips or clamps are found.