Ive got one of the cheapish camera modules coming from spark fun, it seems quite easy to interface its got a pulse line, 8 bit data bus, hsynch and vsynch (and an i2c control interface).
basically when the vsych pulses high, it signal a new frame. When the hsynch pulses high, it signal a new line. when the pulse line pulses, it signal a new byte available on the 8 bit data bus.
I'll probably slow its clock down and use a dedicated pic at 20mhz to interface to it and send the data to ram. Maybe another pic to reduce image size/ convert it to a smaller image for ease of use, and act as a go between.