ThinkGeek ships its TK-421 iPhone case that gives your iPhone a real, physical flip-out tactile QWERTY keyboard. The case has a handy built in keyboard that rotates out when needed for qucik messaging. It use Bluetooth to connect with iPhone, and is powered by its own built-in rechargeable battery.
ThinkGeek TK-421 is available in models for iPhone 3GS and iPhone 4. You can get one for $49.99.