The 2011 North American bee calendar is available from the Great Sunflower Project and the Xerces Society's websites

Since writing about this summer’s squash bee hunt, I’ve received a number of enquiries about how to view the 2011 North American bee calendar that was referenced in my article. The answer is fairly simple: visit the website for Dr. Gretchen LeBuhn's Great Sunflower Project or for the Xerces Society for Invertebrate Conservation.
According to native bee advocate Celeste Ets-Hokin, who produced the first ever North American Native bee calendar in 2010 in collaboration with Dr. Lebuhn, an environmental science professor at San Francisco State University, the bee calendars are a fundraising effort for Lebuhn’s Great Sunflower Project. 
"The Great Sunflower project currently boasts an online membership of roughly 80,000 citizen scientists from across the United States and Canada who have joined Dr. LeBuhn in the hunt for bees," Ets-Hokin said."Members plant sunflowers in their garden and time how long it takes bees to visit, allowing Dr. Lebuhn to collect data on the health of the bee community across the continent."
Sales of the 2011 North American Bee Calendar will continue to support the research of The Great Sunflower Project, as well as the pollinator conservation efforts of the Xerces Society of Portland, Oregon.  Calendars may purchased here and here.  Hope that clears up the mystery! (Apparently, the calendars only went on sale today September 7.) And enjoy learning more about the amazing lifestyles of North American bees!