How to find out someones current address?

Ok was too nice to someone ex renters moved out owing for their last months rent. They think since they moved out before the 30 days was up they dont owe any extra rent. They were given notice on the 20th of the month (Oct) moved out Nov 5th early and do not want to pay. Also did not pay for utilites which I figure they would owe til Nov 20. They shared the house with another room mate so utilites were to be split. Looks like I will need to take them to court to recover. Of course since they were friends of my sons at the time we did not ask for deposit so they felt they did not need to do any major cleaning and were not waiting for me to return a deposit so of course they did not leave forwarding address. They have told us three times the dates they were going to pay us. The last Dec 15th anyway tried to phone and they have changed phone numbers and I do not know the address. Is there a site where it can be found without having to use my credit card or join a service. I will need the address to file for court