From Martin's blog:

With the year running down, we'll all soon be needing new 2011 calendars to hang on the wall. There's still time to pick up the official 2011 Ice & Fire calendar, with its gorgeous castle landscapes by Ted Nasmith.  

If you can't find the Nasmith calendar at that kiosk that appears every Christmas at your local mall, check your local bookstore.

A few copies may also be available through some of the associated sellers on Amazon, though Amazon itself seems to have sold out.

http://www.amazon.com/Song-Ice-Fire-2011-Calendar/dp/0553808001/ref=sr_1_1?ie=UTF8&s=books&qid=1292828522&sr=1-1

Meanwhile -- not to get too far ahead of ourselves -- but work continues apace on next year's Ice & Fire calendar as well. The artwork on the 2012 calendar will be provided by Hugo-award winning artist and fan favorite John Picacio, and he's doing some amazing stuff. So I thought I'd whet your appetites by showing you the mockup of the cover that Bantam featured in its latest catalog. 

The Picacio calendar will be released next July. This may not actually be the final cover, but it should give you a good taste of the spectacular work that John is doing. He tells me he's determined to make this calendar the best work he's ever done.

So... who would you guys like to see do the art for future calendars? Our plan is to feature a different world-class artist every year.

George  R.R. Martin