These are a few Q&A here to get started:
Using the camera activity in Android
Use camera flashlight in Android
Android camera intent
How do I save data from Camera to disk using MediaStore on Android?
And some tutorials out there:
http://mobile.tutsplus.com/tutorials/android/android-sdk-quick-tip-launching-the-camera/
http://2008.hfoss.org/Tutorial:Creating_a_Camera_Application
http://www.androidph.com/2008/11/camera-capture.html
http://code.google.com/p/openmobster/wiki/CameraTutorial