I am surprised that I haven’t come across a voice based classifieds system. Well creating one from scratch and reaching critical mass is difficult, but leveraging social media and Craig’s list should not be difficult at all. So, here’s the idea. User calls a premium number and speaks the advert. The server processes the voice and tries to understand the message. If the message is correctly understood, it will post an appropriate ad on Craig’s list, with the user’s phone number and an auto generated email id.