Car Overheating: Possible problems and fixes?

I was driving my car, (Subaru Outback) and got a phone call so I pulled over to talk, and right when I did that i looked up and my car was smoking. It shut off, and I noticed that the temperature gauge was all the up. I let it sit for a while and it cooled down. I figured it was from low coolant. I picked some up, and let my car sit for a while. I filled up the reservoir with water as a temporary fix, and then filled the radiator with actualy coolant. I let it sit over night and drove it for about 15 minutes in the morning to see how it would act. It was fine for the first ten minutes but then the temp needle rose all the way up again, but this time there is no smoke coming from my hood. I also noticed a leak coming from my radiator (or in that area) but I have no idea what the problem could be, and any possible fixes. Help Please!