Craig Newmark is the founder of Craig's List (spelled craigslist), a site that provides free classified ads for people in more than 200 cities around the world. Started in 1995, it is now one of the most visited sites on the internet.

Craigslist includes notices for public events and only charges a fee for job and real estate listings in some large cities. The organization and Craig in particular are notable for both their groundbreaking work in making Web 2.0 usable for everyday purposes and their support of non profit organizations.

One of the most important things to understand about craigslist is its success with usability, as is evidenced by it's huge number of participants. "I had the advantage," Craig says, "of not knowing what I was doing in the begining." I asked him for tips on maximizing usability and he suggested "nothing fancy, just text, give people what they want to see - use fonts, background colors and don't get in the way."

Craigslist is a great example of a site that derives its value in large part from "user generated content." This model was first employed on a large scale in a commercial context by Amazon.com through their use of reader reviews and recommendations. I asked Craig if he had any thoughts for non profit organizations considering a user generated content approach to their web presence.

"Presuming that the purpose is to share good ideas and news," he said, "the most basic step would be to install a good discussion board or a wiki." He is of the belief that such an infrastructure will naturally be populated by user contributions if it is simple, well designed and fills peoples' needs.

Content on craigslist was used to create one of the first and most visible mash-ups online, housingmaps.com. This combination of craigslist housing listings and Google Maps offers a way to visualize the results of a search for homes in select cities and was the inspiration for many mash-ups afterwards. See, for example, CoolGoogleMaps.com.

Craig said that this use of his company's data is something that they are appreciative of because it fulfilled a function that the company has been unable to prioritize providing themselves and was designed in a way that hasn't overburdened their resources like server load.

On the craigslist site itself, Craig said that one future development in the works was a technological way to deal with users who over post or make redundant posts. Popularity has brought its own problems and the service may begin charging a fee to apartment brokers in New York, for example.

When I asked Craig wether he thought Web 2.0 as a concept was real or hype, he said that it is a mix of both. The most exciting development to him is the way that new technologies are allowing different sites on the web to work together. He said that as soon as he can hire some more people to do customer service, he is going to learn how to use AJAX, or asynchronous javascript and XML - as seen throughout housingmaps.com. That will allow multiple sources of information to be integrated in a way that's fast and easy for users.

You can find a list of all the cities that have local craigslists at craigslist.org
Craig Newmark's blog is at cnewmark.com
The Craig's List Foundation is at craigslistfoundation.org