If you consistently contribute on the site by answering questions and blogging then this will give you very good exposure which helps in establishing you as knowledgeable and the "go to" agent in your market area. The key is consistency and being helpful and not just repeating what others have said but give something of value. This should get you some leads in your area. However; do know that some market areas are more popular than others so garner more people actively using the site.
Trulia is a highly ranked real estate web site so give it a try.
Good luck to you!
Prudential Connecticut Realty