Great question! Like stated in a previous answer, you have to list with a brokerage to be included. Finding the right broker/agent is the key. Listing with an broker/agent is the next step. Many brokerages include posting your listing to the major sites (Trulia, Zillow, Realtor.com). When you start to interview brokerages/agents...ask that question. If they charge you more to list on these sites, move on and find someone who includes it in their services.