Criagslist, Craigslist, Craigslist....
One word of caution, make sure what ever you buy will pass emissions. I also recommend a common car, since a $1000 car will need parts some time and you don't want to be paying crazy prices for parts. I had a 91 VW Jetta and I was getting 30 MPG. I do NOT recommend any VW newer then 93 since the transmissions are know to break and they are very expensive. Honda Civics and Accords are also a good choice, but I was told by the guy that I go to for emissions to avoid Nissan, Mazda, Suzuki, Kia, and be careful with Toyota's they are hit or miss.
Living in SE CT I also recommend front wheel drive, much better for the days when it snows and you are already at work.