Dark Roasted Blend has a great article on turtles right now, complete with tons of great pictures and some interesting facts about the creatures. For example:
The rigid shell means turtles cannot breathe as other reptiles do, by changing the volume of their chest cavity via expansion and contraction of the ribs. Instead, turtles breathe in two ways. First, they employ buccal pumping, pulling air into their mouth, then pushing it into the lungs via oscillations of the floor of the throat. Secondly, by contracting the abdominal muscles that cover the posterior opening of the shell, the internal volume of the shell increases, drawing air into the lungs, allowing these muscles to function in much the same way as the mammalian diaphragm.
I don't know about you guys, but this article makes me want to run off and adopt some new hard-shelled pets.