The Democratic firm Public Policy Polling was in the middle of conducting a poll on the NY-23 race when Scozzafava dropped out. It showed conservative Doug Hoffman beating Democrat Bill Owens by 19 points--but it didn't yet have a full sample. PPP writes on Twitter:

With about 200 interviews down we had Hoffman 45 Owens 26 Scozzafava 17...her withdrawal will just make it that much easier for Hoffman

Of course, as noted below, the independent Siena poll showed Hoffman trailing Owens by 1 point.