Would you want a force-feedback stick? If so Logitech just released the Wingman Force, the best force-feedback stick on the market. It's only about $100 (cheap as hell for a force stick) and has recieved great reviews everywhere. If you don't want a force stick, you can get a Microsoft Sidewinder 3D Pro for around $40, or the USB version for about $65. The best thing to do is just to go to a computer store and try out all the sticks there. Simply pick the one that feels the best for you.
Thrustmaster and CH Products makes some excellent flight/joysticks but they are not widely available. I just bought the Thrustmaster TopGun Platinum joystick for $25 and am very happy with it. It has four buttons, a 4-way toggle button, and even a throttle built-in.