Beeing (hahah) its National Pollinator Week thought I put up some links to some cool website. Like Save the Bumblebees, http://www.savethebumblebees.com/. It has links to keys and other helpful information.
Looking for images of bumblebees? Check out Bug Guides image gallery for the genus Bombus.
Another cool site on pollinators. North American Pollinators Protection Campaign.
and The North American Pollinator Protection Campaign and The Pollinator Partnership