Over last few years a lot of people keep asking on how to connect the OV7670 FIFO module to Arduino Uno or Duemilanove.
I will start by saying that I do not own an Arduino Uno board or any other Arduino board except 1-2 old Arduino FIO and I use them only to charge some LiPo batteries.
Also, I am not a big fan of using Arduino for such project as the use is pretty much limited due limited number of pins available, performance of the Arduino code and UART speed. However, with a proper cpp library some things can be done.
Anyway, the schematic should look like:
There is no need to use all the pins on the FIFO module unless you have an application that takes advantage of them (e.g.: OE and HREF). Also, using only D4-D7 and connecting them to A0-A3, switching to YUV mode then capturing D4-D7 for every Y byte will increase the speed (using 4 bits/pixel instead of 16 will reduce the amount of data from 38400 bytes to 9600 bytes for 160 x 120 pixels frame (from 11 seconds transfer for a frame to around 3 seconds @38400 bps).
Update Feb 2015: The software for this schematic is available here.