the audience on craigslist is amazing, and its local. i sold a gas motor today from an old remote controlled airplane. it was at a really good price so someone responded in about 15 minutes of it being posted.
craigslist is a web example of real value. it does classifieds better than the newspaper. its an online catalog with a real-world component. its also an altruistic model - the job listings cost money to the advertiser. all other postings are free.