Wash cranberries; pat dry. Place cranberries in a clean 1-quart jar. Pour vodka over fruit. Cover jar tightly with a nonmetallic lid (or cover jar with plastic wrap and tightly seal with a metal lid.) Let stand in a cool, dark place for two weeks. Keeps up to two months.
To serve, pour vodka and some of the cranberries into small glasses. Garnish with lemon slices, if desired. Makes 16 (1-ounce) serving.