'91 Corolla with coolant/antifreeze leak

I have a 91 corolla and noticed in the snow the other day that there was coolant on the ground after I moved my car. The next day I filled the coolant which was empty and then drove home. I drove my normal half an hour to work and when i got there I checked the coolant and it was half gone. I openned the hood and turned the car on since my roommate told me that he saw coolant come out as I was pulling out in the snow the other day, but everything seemed dry and I couldn't see it leaking anywhere. I went out a little later to see if maybe the actual coolant holder was leaking and everything in the engine still seemed dry. Does anybody have an idea as to what's wrong? The heat works fine and I never go above a quarter on my engine temp gauge. I also don't know if the coolant is half gone simply because it replenished what was needed in the radiator since the coolant was empty when I put it in the other day.