When I take a picture with the camera on my iPod, the lower left of the screen is a button that takes me to the photo I just took. If I click on that, then the photo appears and on the bottom of the screen is a menu with four buttons. Sometimes that menu disappears but when it does I just touch the photo anywhere and it comes back.
On that menu, the first item (from the left) is a blue camera that takes me back to the camera. The second is something that looks like a "forward" icon. If I hit that, I get a bunch of options of how to send the photo somewhere, including Mail, Message, Twitter, Facebook, and other stuff.
I don't remember it being any different on my wife's iPhone (4).