free because it is supplied to us by people like you and me.So if your are looking for something or wanted to know about something you can source the information via the internet. One very handly free service is provided by Aardvark.
Aardvark provides a service that helps you find the answers to your questions, it attempts to get answers to you from reliable people, send questions to others that have tagged their profile to answer those types of questions or who feel they can contribute.
Crowd sourcing comes easy here, because the more you participate, the more you benefit the larger community. So its simple.. you ask question where you do not have the answers and you answers question for which you have the answers.. Try it to know it better..
By the way, an update: In February 2010 Aardvark was acquired by Google, and continues to operate as part of the Google family of products.