Has anyone tried online classified ads, like from newspaper websites that have free online listings or paid ones too and how effective were they for your online marketing purposes?

Did they give a good boost in rankings?
Did they give good click though traffic?
What newspaper sites worked good ones for you?
Anybody have a good list of classified ad sites?
Anyone does this service, online classified ad submissions, just like what raj and sunil does for directory submissions?

Any kind of input will be greatly appreciated.