Wormwoods, just down the way in Cape Ellis. Huots at Camp Ellis is good, too! (However, you might want to re-post your questiong, Southern Maine is not "Southern New England")
When you said Southern New England, I was gonna recommed The Hingham Lobster Pound in Hingham, Mass - it would be QUITE a trip from Saco, Maine tho! : )
This will probably get moved to the Northern NE board....anywho, my favorite seafood place in southern Maine is Fisherman's Catch in Wells. Just a little south of Biddeford.