Only a REALTOR may upload listings to Trulia. Since you are in the MLS, I assume you are working with an agent, or at least a limited service brokerage. If so, just ask you agent to visit the hyperlink below to upload the listing. Trulia is fairly new, and there are many great REALTORs out there who are unaware of it. Help us spread the news! Tell your agent. He/she will thank you for it!
Postlets will only post to Trulia if the posting is made by a licensed broker. Trulia does not accept listings from FSBOs.
Ecmeister, your Realtor will be able to submit the listing for you. It does not automatically pick up all listings from the MLS; they must be submitted through an automatic feed (i.e., my broker, Keller Williams has this), or manually by your agent.
Pass on the link provided to you below by Bridgett.