Remerica Hometown One
Trulia uses feeds from the different multiple listing services. If you're not on an MLS that feeds into Trulia, you can't get listed.
Some agents will put your listing on the MLS for a nominal amount--often in the range of $200 to $300. And, incidentally, you should do that whether or not Trulia's important to you. There are plenty of people in your area who are using the MLS through other agents' sites, through Realtor.com, and so on. NONE OF THEM are running into your listing.
Hope that helps.