The most effective place to post a home for sale is your local Multiple Listing Site. These sites are created and owned by the local agents and brokers, so access to them is limited to using an agent. Sites like Craigslist and Zillow will allow you to post a For Sale by Owner, but the exposure will be minimal by comparison. You can also advertise in the local paper and other sites, but all combined they can't really compare to what being on the MLS can do.
Trying to bypass an agent makes sense at first, but as you realize how much is involved, the best and most effective exposure, the legal issues, the negotiating knowledge and experience a great agent brings, the thinking begins to breakdown.
Notice, I mentioned a "great" agent. Too often the public hires an inexperienced or ineffective agent and things go wrong. Then they assume that all agents are equally inexperienced or ineffective. This is truly an 80/20 or even 90/10 business, where 80 to 90% of the business is done by 10 to 20% of the best agents. If you focus on finding a truly outstanding agent rather than trying to learn our business, chances are you'll make more money, be safer and come out altogether better in the long run.
If you want to try on your own, Trulia doesn't accept FSBO's but the other sites I mentioned do. Best of luck.