YouTube

I listen to YouTube all the time but never have I thought about creating an account. Now I have one that I am going to use all the time. In the past, I used to search for one video, watch it and then pick the next one to watch from the right hand menu. If I ever randomly stumble upon one that I like, I need to look for it the next time which could take few minutes. Now, and with one click, I can add it to my favorites and watch it later with no need to search. Also, if I ever end up having too many videos saved in my favorites, I get to create a playlist which sort videos by a specific artist or genre.
As for a business, I think YouTube would be a very effective advertising method. Although, it will require more work on the part of the business compared to a Facebook page or Twitter, the payoff could be way more since customer like visuals rather than texts.