As others have already indicated, it depends upon which MLS you are affiliated with. Jay is correct that we receive TARMLS listing information via Listhub so long as you are opted in to have your listings included in their feed.
Also, please keep in mind that we don't just receive listing information via the MLS. It is also syndicated to us from other sources like Postlets, Point2Agent, vflyer and z57, to name a few.
And you can always submit your listing to us manually via the link below. It's easy to do and your listing will be live on Trulia within one hour.