consumer cameras typically save the image in jpeg format, and use USB as an interface. Adding USB to your project is not too complex, but handling an image file becomes more difficult because of it's size.
I have no idea what the scope of your project is, but you might consider using a micro with USB to control the camera, then act as a hub to pass the file onto a more capable system for image file operations.
The beauty of consumer type cameras is thier low price for yesterday's models. The Canon A510/520 for instance can be had for under $40 from Ebay. These cameras allow full control over the USB port, with the exception of off/on. I overcame this by mounting a surfacemount transistor across the on/off switch, then connecting the base of that to the unused USB pin. My controller consists of an 89x5131 Atmel along with a Max3421 USB host driver. The micro, under a variety of trigger conditions, turns on the camera, then issues commands via USB, which can include zoom, image capture, viewfinder image stream, etc. The images are held resident in the cameras storage. When connected to a PC, the micro acts as a hub between camera and PC to allow normal image transfers.