National Geographic is offering their 2006 Penguin calendar free($5.95 value-it's on sale too) with purchase of a March of the Penguins DVD.
Just add the DVD to your cart and the calendar is automatically added.
There's a typo on their page--as it says 2005 calendar on one line and then 2006 calendar on another. They confirmed it is the 2006. They'd have to pay me to take a 2005 calendar!
Shipping is $4.95 for their ground option.