Where to sell used office furniture in san bernardino or riverside counties, ca.?

Yes, you should absolutely start with Craigslist and I would also try ebay. Lastly, depending on how much money you are trying to get and whether or not you are willing to pay a small fee, I believe Almost Free Furniture (I think their domain is almostfreefurniture.com and there is also a link on my site) will let you list used furniture with them as well as buy it. While online is usually best for selling used anything these days, you should also look at what print resources you have available: local papers, local trade publications, and even local physical message boards for announcements, etc. (check supermarket entries). Hope that was helpful to some degree. Sincerely, The Furniture Guy Lead Writer, http://furniture-guy.blogspot.com/