From the help screen...
Choosing what application opens when a camera is connected to your computer
iPhoto works with Image Capture, an application included with Mac OS X, to transfer pictures from your digital camera to your photo library. When you open iPhoto for the first time, you're asked if you want iPhoto to open each time you connect a camera to your computer. You can also choose a different application.
To choose what application opens when a camera is connected:
1
Make sure no cameras are connected to your computer.
2
Open Image Capture (in your Applications folder).
3
If you're using Mac OS X version 10.2 or later, choose Preferences from the Image Capture menu, then choose an application from the Camera Preferences pop-up menu.
If you're using a version of Mac OS X earlier than version 10.2, choose an application from the Hot Plug Action pop-up menu.