Sometimes Penstemon barbatus and Penstemon eatoni get confused, both being tall scarlet-flowered penstemons. I don't currently have a good photograph of Penstemon barbatus, but I'm showing a couple photos of Penstemon eatonii taken in my garden in 2009. These photos are slightly out of focus, sorry about that, but at least they depict the downcurved-arched disposition of the flowers on Penstemon eatonii, as opposed to the straight "shark-tubes" of P. barbatus. If any forumists have a good photo of P. barbatus, in any of its color forms, please post them here.
USDA Information page:
Lots of excellent detailed photos on the CalPhotos site:
This gorgeous photo clearly shows the downcurved arch shape of the flowers on the Eaton Firecracker: