There are some great prices for Trans Atlantic crossings on Cunard's (www.cunard.com)Queen Mary 2 this fall and winter. Rates for the seven day crossing between New York and Southampton start at only $699 per day per person, or about $100 per day. Considering that this includes your cabin (probably inside) all your meals and lots of free entertainment, it is hard to beat.
These deals are available on sailings on October 27, November 19, and January 3. This could be a nice treat for Thanksgiving or to see in the New Year. The Atlantic can be rough in winter, but it can also be bad in summer--it's all part of the sailing experience.
While I have yet to sail on the Queen Mary 2, I have crossed twice on the Queen Elizabeth 2, her smaller sister, and enjoyed both voyages a lot.
If you prefer to sail along the coast of New England and Canada and down the St. Lawrence River with its great whale-watching opportunities, the Queen Mary 2 is offering even better rates for inside cabins on its Oct. 15 sailing from New York. The cost for a 12 day cruise starts at only $799 per person. Teh ship calls at Newport, Bar Harbor, Boston, St. John, Halifax, and stays overnight in Quebec City.