We are trying to sell our home here in Brazil and I have listed it in various places including here on Hubpages. That makes it convenient, and then I use Twitter to promote it. If you have a large network, such as on Facebook, let them spread the word for you as well.
I know you said you want free classified ads but I also listed my house with an agent, who does 'for sale by owner'. There is a one off fee and they list it on places like Rightmove, the Movechannel and several others.
Others I have listed with are:
Kugli (Easy to use, and I get quality emails from them)
Stay away from Best Abodes as I have had so many scam emails from ads I have placed with them.. Some will say they are free until you get a response and then ask you to pay. I believe those are also scams. Free is Free.