mysterious battery drain?

I recently had to purchase a new battery and I'm experiencing a overnight drain. (the old one was just bad) I remember when I first got the car, leaving the cellphone connected would pull on the battery overnight. But I haven't had the phone connected in months. I had my alternator tested and found out it was faulty. It's been replaced. I don't drive this one every day, but may twice a week. Anyone know what else could be draining a perfectly new battery leaving the car a few days in the garage?

thanks