Outside of the rental websites, Craigslist and the local paper, your best bet is using a local REALTOR, particularly one who specializes in multi-family homes and rentals. They routinely work with investors so they always have their "ear to the ground" for new opportunities.
I'm currently carrying a couple of rental properties myself. One is a 3BR, 2.5BA house in the Mt. Carmel section of Hamden and the other is a 2BR, 2BA townhouse-style condo in the Westville section of New Haven. If you'd like more info, please email me at EmbarkWithMARK@GMail.com.