My car stalls every time I slow down at a light, while Im driving, sometimes while I turn. What could the problem be?

First of all, to help you we need to know the year of your car, what size engine you have, and the mileage. Also, if you could describe the symptoms you have in greater detail, i.e. does it sputter and die or just flat out shut off? That information would help us help you.

<edit> also, do you hear any abnormal noises or notice smoke?