How do you wire up the OV3640 camera module?
The i2C interface is just to configure the image sensor's parameters. The actual image data is blasted out the parallel camera interface (called CAMIF), which consists of an 8 to 12 bit parallel data bus, plus horizontal and vertical sync signals and a pixel clock. The pixel clock tends to run at 50-100 MHz depending on resolution and framerate, so your microcontroller will need to have a hardware CAMIF module to handle the timing. Many high-end Cortex-M4 and Cortex-A processors from ST, Freescale, and TI have the hardware necessary for this. Obviously, an FPGA/CPLD could also perform this functionality.

You'll also need quite a bit of free memory to hold the frame(s) you grab from the image sensor -- a 2048 X 1536 image, in RGB888, will require ~9.6 megabytes.