The Sam Adams Winter Classic selection is interesting and very tasty this year. The Cranberry Lambic is unique, but whether it is a true Lambic or not I cannot say.
Here's a review of the selection at Fermentedly Challenged.
(Disclosure: The Boston Beer Co. was kind enough to ship 1000 cartons of Winter Classics to Maggie's Farm as a neighborly thank you. That should get us through December, anyway.)